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Discussion Starter · #1 ·
Just started dosing P in the form of fleet enema. My math and what others say leads me to believe that I know that amounts I am dosing. ! drop from the "appilcator" is approx. .1 mg/l in 10 gallons. I dose 5 drops, check it an hour later and I am only up .1ppm. I shake it well before dosing. I am wondering if my plants were really starved for P could they take it up that fast?
 

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Hi Dennis,

I can't say for sure about the takeup in 1 hour. I was using .1 ppm P for a while, but since Tom Barr has been proposing it I have been using 1 ppm P. I was using an enema for P and using the pipette that comes with the Flourish products. I never trusted the drop method since the applicator for the enema has such a wide opening. I now use KH2PO4.

My web site also has some calcs for the generic Fleet enema at:
http://users.ev1.net/~spituch/Chemicals/chemicals.html
I have a note saying that in general .3 ml enema will raise the P 1 ppm in 10 gallons.

What kind of test kit do you have? I do not trust test kits, or myself using and interpreting one. I would just figure it out and measure it accurately.

Regards,

Steve Pituch
 

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Back in the day, when Steve Dixon first began dabbling with P supplementation, Claus Christensen spoke to sfbaaps. He was asked his expert opinion on the supplementation of P. He noted that, and I paraphrase from 3 year old memory, P is a mobile nutrient in aquatic plants and is stored much like mammals store fat. In a few hours aquatic plants are able to take up enough P to last for several weeks growth. It was his opinion that maintaining measurable P was a misleading practice and he even suggested that excessive P was as bad for plants comparing it to excessive fat in mammals. He asked us, why we would want obese plants?

Tom Barr has recommended 1 ppm of P and cites studies that suggest aquatic plants are less effective in reducing P than algae. These studies are made in considering natural conditions to learn how humanity can reduce the amount of P pollution in our streams and lakes. Excess P has been associated with the loss of global coral that is considered a negative impact of human activity. These studies may not be applicable to our enclosed environments where we are able to influence P uptake by changing ratios of N.

Barr noted that 1 or even 2 ppm of P really caused no major algae problems if N was maintained. He assumes it can't hurt and seems to be correct so long as N remains measurable. However if P functions as Christensen claims, maintaining measurable P may not be necessary. It may in fact make one a slave to N supplementation.

Jeff
 

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Plants need more PO4 than algae from A RATIO PRESPECTIVE but at low levels of PO4, the plants cannot remove anymore. Plants also cannot utilize the organically bound PO4, wereas periphyton can.

I suggest certain ranges etc, but these are not written in stone nor are any ratios.

The ranges are suggestions based on folk's dosing routines. Though weekly would be nice, many folks run CO2, more light etc and more frequent dosing is needed. I've tried to make it through a week at high traces, PO4, NO3 etc but the results are not as good as every 2-3x a week. Daily did not really show much improvement in plant growth even at 6 w/gal.

What the levels are dosed to is another issue. Plants are pretty flexible. They can take up more PO4, NO3 etc than they need as can algae. The richer dosings allow for some wiggle room, leaner methods allow for less wiggle room. This might not matter at low light, but at higher light, it'll become more critical.

But a small pulse every few days like the traces added every 2-3 days etc and have the residual allowed to go zero is fine also. Maintaining a range over a time period is better than attempts at maintaining a precise stable residual amount(A lesson in futility).

But I think the notion that the algae are limited somehow and the plants are not, is outdated nor is it correct in isolated studies that look specifically at algal limitation ranges.

So it might be simpler to dose more than less.
Everytime Ive made sure that the other parementers like CO2, NO3 etc were non limiting, I've found some wide ranges of nutrient values that all work.

You can dose less and more frequently, you can dose more and less frequently, you can dose more than is needed etc all with good results. Having fish etc will allow you to rely less on dosing.

But as far as being a slave to dosing, non CO2 tanks are hard to beat, add fish and fish food only and top the water off. The CO2 addition is going to drive faster uptake of everything. Perhaps the PO4 is quickly removed vs the NO3, but NO3 uptake is greatly enhanced(1ppm vs 3ppm a day for example) by adding PO4.

So you can pick which ever plant nutrient you want to pick on but they all have that effect on the next nutrient down.

As far obese plants, I think there's been a fair amount done on plants from high PO4 waters, I'm not sure what is meant by obese plants and "fat". I don't think it's bad, but I also agree that plants can take up a lot fast and have a good reseve for awhile, but the issue is the form of PO4. Inorganic forms are the only types used by plants.

You can try the dosing of PO4 at high light under non limiting conditions and use O2 as a measure of production. You will find after 2-3 days a decline, perhaps not at lower light, but at higher lighting, this was true each time I've done this.

O2 measurements are often used in terms of production, so that's growth, not "fat". But PO4 limitation does not cause the nutrient deficiency symtoms that many other nutrients cause so it's not a bad one to allow to get low.

I find no negative issues with more PO4 than is needed, just like more CO2.

Plants don't need CO2 added either...............but it helps improve their production........

Regards,
Tom Barr
 

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Can you please elaborate on why can't plants remove more PO4 when its concentration is in the ppb range?

Thanks. Sorrry if I've strayed too far from topic.
 

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Discussion Starter · #6 ·
I probably should not chime in to loudly here because I thnk plantbrain knows a heck of a lot more than me but I really do agree that more seems better than less. Whenever I have tried to limit a nutrient to help combat algae, it only makes it worse. Having higher concentrations though do not seem to go south as fast. I used to try to keep NO3 at 5ppm and P in the .5ppm and Fe at the .1(and yes, that is an exercise in futility. Arrrgggg:) )My tank quite a bit richer and am happy that i do. NO3 5ppm, P 1-2 ppm Fe and traces I dose every day 1-2 ml(using Flourish and Flourish Fe) and I really have gotten rid of most of my algae. If I get lax, or busy and one of the Macros(including CO2) bottoms out, bam, algae. Water change and redose, everything is ok in a day or so again. The only real algae that i get now is thread algae, mainly in the finer leaves of the R indica. I attribute it to the larger doses of Fe and traces but my plant growth is also incredible so..... IT only starts to appear towards the end of the week anyway and then it slows down wiht my usual 50% wc. So yeah, my observations are that higher levels of all nutrients (within reason of course) ssems to produce no ill effects fo me while letting any single one get low tends to create algae and slow down plant growth (of course this is why the algae appear right?).

Just my 2 cents.
 

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plantbrain said:
As far obese plants, I think there's been a fair amount done on plants from high PO4 waters, I'm not sure what is meant by obese plants and "fat". I don't think it's bad, but I also agree that plants can take up a lot fast and have a good reseve for awhile, but the issue is the form of PO4. Inorganic forms are the only types used by plants.
What are the standard sources of inorganic P in a low light tank, then? New water? I assume most of the P from fish food is organic.

Might low-light tanks benefit more from P dosing than high-light, CO2 tanks?
 

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I do not dispute Tom Barr's premise: that 1 ppm P is beneficial and is risk free. What I dispute is the collective reading of that premise that assumes that if 1ppm is beneficial then maintaining 1ppm is even better. Or as Dennis Dietz states "more seems better than less".

It is precisely this attitude that I think Claus Christensen was referring to when he made his obesity metaphor. For those of us born and raised in the United States such an idea makes perfect sense; we are accustomed to gluttonous consumption and feel perfectly justified with its practice. However, I believe Christensen was a making more of a cultural point than trying to make a supportable analogy.

If Christensen is correct in his claim that plants take up enough P for two weeks growth in a few hours then maintaining P is not necessary. Note that Dietz's original observation supports Christensen's claim and also note that Barr specifies that a known range of concentration is the goal, not stasis. Our tanks are dynamic environments and trying to impose "scientifically" some static condition is, as Barr points out, "A lesson in futility".

Many people promulgating what they call the "Barr" method and who recommend maintaining 1ppm P are in fact promoting a new premise: the phosphate dominant tank. I consider this type of tank relatively high maintenance and most definitely an advanced practice; this is not appropriate advice for newbies. Those of you who have neglected a P dominant tank know how fast they go down hill if they run outa N. These conditions leave very little room for error with low N.

If Christensen is correct, better advice would be to provide a calculated 1ppm measurement of supplement with each water change interval. This would reproduce the magical Marin water district phenomena that was the basis for considering P supplementation while mitigating the problem of running low on N. Regardless of additional data, in support of his original premise, that Barr discovers as he increases his knowledge base, what is still most important is the original observation.

To really understand aquatic supplementation requires an understanding of the interaction between N and P. This was the investigatory basis for Barr's premise and it has an interesting history but I've run outta time for this post and will get back to that later.

Till then...

regards, Jeff
 

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Discussion Starter · #9 ·
Very well thought out Jeff.

Here are some of more of my thoughts. First being new to this I missed alot of the earlier research from folks like Barr and Christensen so if I am in error with something, or I drag up something already known, sorry. I personally do not know much about the relationship between N and P, except that I have found them to be very closely connected. Tom Barr's "ladder effect" illusrtates this well. An increase in P dosing generally leads to faster uptake on NO3, which leads me to a question...

Does an increase dose of P, or any other nutrient for that matter, directly increase the uptake of other nutrients because of increased plant growth? Or is there some other factor involved I am unaware of? Is there a limit(obviously there is) to ho much we can increase the growth rates of plants or is it, at least to a degree, based on the nutrients they have avaliable.

I think one thing we really need to keep in mind here is that we are talking about high light, and more importantly I think, higher CO2 levels. At these higher level, eventually we will become slaves to some nutrient. Say you keep your macros plenty high enough(using low light ideas here)but dose nothing else. At the increased growth rates from the CO2 and light eventually some trace(s) will become th elimiting factor. AM I right here. It seems to me that we are making ourselvs the slaves to a nutrient not by trying to limit one but by increasing CO2 and light. To me that is part of the fun though:)

Tom Barr wrote "So it might be simpler to dose more than less.
Everytime Ive made sure that the other parementers like CO2, NO3 etc were non limiting, I've found some wide ranges of nutrient values that all work". I have found this, in my limited experience, to be completely accurate. I was always fighting algae until I started dosing P to 1-2ppm at wc and check it mid week, although if Claus' findings are correct I do not need to check (although I find spot algae greatly increases wiht very low P levels) because there should be enough P to sustain them. This would explain though how initially I could dose 1-2 ppm P in the morning and at night it was gone. Hungry plants, american plants:) eating more than they need.

I would love to learn more about the N/P relationship. Any suggested reading? Also, a quick thought from me. I originally though that algae came from an excess of some nutrient but know I am thinking that it actually is a result of excess of many nutrients as a result of slowed plant growth due to a deficency of one nutrient. Does this make sense or am I once again missing some point? I have trouble grasping the excess=algae theory in the basic sense because if excess was the problem, why would it slow plant growth. I thought hte resaon we could keep algae at bay was because plants are able to out compete the algae for nutrients. However, if a nutrient is deficient,then it seems the algae, a simpler organism wiht simpler need, would not be slowed as mucha s the plants and thus start to thrive.

Just some thoughts.

Tired, must sleep now:)
 

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Dennis,

First of all, thanks for starting this thread. I was wondering about P myself.

Like you said, there is clearly a limit on the speed of plant growth. I think the entire nutrient regiment should be tailored to be just below that threshold, to prevent unusable excess for accumulating and causing problems.

Problem is, I think, that there are just too many species in a planted tank (usually) for the aquarist to be able meet these requirements consistently. One notices a problem with Lythraceid plants and doses more Ca, Echinodorus are yellowish and more iron goes in, another deficiency leads to another and so on and so forth. Obviously nutrients affect the uptake of one another, as you pointed out. The "relationship" between K and Ca comes to mind.

I believe the best way really to do things is to find species with very similar nutrient requirements and maintain plasticity within your ferts until a balance is reached. Tom Barr I think has the best idea in this regard...more is better than less, in most cases, but you still can't please every species with the same conditions.

As far as the conventional wisdom about algae, I believe algae probably need just as many nutrients to survive as plants do, but in different ratios. This I believe is the basic premise behind algae prevention. You don't necessarily have to limit P per se to kill algae, but anything really that the algae needs but the plants can survive on less of can be manipulated to deal with it appropriately.

There is definitely a synergy present among nutrients, and finding that balance is key to algae control. IMHO, of course.

Disclaimer: I may in fact have absolutely no idea what I'm talking about, so let me know if that's the case.
 

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I came to aquatic gardening in 1997 when Aquatic Plants Digest was a primary source of current e-formation. At that time the Sears/Conlin PMDD practice was widely accepted along with the premise that P limiting would yield success. In my enthusiasm to find a recipe for success I insinuated myself on Steve Dixon and attemped to follow his PMDD practice. It was complex, difficult to calculate, required test kits and generally tried my scientific training, my ability to absorb data, and my patience with getting the results I dreamed of.

When TMG became available through Monolith Marine Steve gave it a try and almost overnight was doing better than he did with PMDD. It seemed that 20$ for 250 ml was a small price to pay for such success and I soon mimicked his practice. TMG supplementation meshed very well with the husbandry skills that I had developed previously by keeping fish with water lettuce, Hygro poly or a solitary amazon sword.

After a while Steve tried KNO3 stump remover (there are several brands other than Greenall brand; tho flammable type stump removers seem to dominate on shelves now) and the results were very exciting. I was reluctant to put chemicals into my tank that might endanger my fish but his fish didn't die and his plants grew better. What we discovered was that measurable N would disapear very fast the first time it was added and improved results were noticed over night. We were easily lured into thinking "more will be better", and it was ...to a point.

Eventually I began to have trouble with plants like Hygro poly while Steve was struggling with several species that Tom Barr had little to no trouble with. At that time all Tom had to do was change water to have success with plants which we considered rare and difficult. We wondered why we worked so hard in comparison. The discussion on APD paralleled our experience and slowly people began to question the P limited premise. Steve with his test kits in hand went out to test Tom's conditions to learn why he had it so easy while we struggled. He discovered 1 ppm P outa the tap at Toms.

Our success before adding KNO3 was entirely related to understanding the dynamic momentum of our tanks. What happened in adding KNO3 is that we depleted the reserves of P in our tanks beyond our tanks momentum to replace it. Before discovering monobasic phosphate we learned to restrain our additions of KNO3 to keep pace with our tanks momentum so that we would not outstrip P reserves. Here is a sample of my tank from that period: <http://www.e-aquaria.com/exp_jkropp.html>

Since the rate of N uptake was determined by P availability we could determine how P limited a tank was by how fast the N was removed. Methodical trial and error combined with N testing and methodical husbandry trained my intuition to practice restraint with supplements. I developed a method that responded to the dynamic natural forces in my enclosed system and was rewarded with wonder at its balance.

To my habits, a phosphate dominant method seems to impose a static psudo-scientific ideology that stamps out the miracle of a tanks dynamic presence. Driving a tank faster than its biological load would be predisposed to, with a desire to maximize growth, seems like a totalitarian sort of desire to dominate. When this standard is promulgated to newly interested aquarists I cringe.

Giving ppm stats and expecting test kits results from participants in forums like this encourages attitudes of exclusivity. The PMDD method and an overt emphasis on speculative science drove by far more people away from the APD than it ever helped to succeed. I know that giving some commonly accepted target ppm readings is much easier than trying to coach each new aquarist in the minutiae of aquatic supplementation but please don't drive them away with data. Let's try to wow them with reproducible miracles of natural husbandry that will enrich their lives.

Jeff
 

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For those that don't know, Jeff and I know eachother and have for some years now. He has a very high regard.

As far as plants being unable to use oganic forms, the organic forms are slowly broken down and remineralize from things like fish waste, but this is slower process than simply dosing a known source of inorganic SRP. Algae have first dibs on these sources which play a role at lower total PO4 levels.
This why you measure 0.0ppm of PO4 and get lots of algae. the PO4 is used up much like NH4 before it's able to be measured. This is a PITA in the field also for both of these nutrients.

Algae are much smaller and live in the water column only. They have much lower needs and variation in some nutrients in their environments.
Typical ratios of dry weight: FW Algae, 14:1 FW macrophytes 10:1, N:p.
Algae have more "sensitive" uptake enzymes, they do live in a different environment than macrophytes do. They are not the same habitat, many assume they are.

When measuring lakes and PO4 levels, the researcher have over looked measuring the PO4 locked in the submersed plant biomass. When that is taken into account, there are polluted lakes can have lots of plants/weeds and no algae. We see this here in FL all the time.

You can mee the needs of a planted tank(CO2, good light etc) at dosings of .2-.3ppm 2x a week if you also have a fish load that's fed well. Similar reductions for NO3 also when having fish loads.

Fish loads, plant biomass/type and health are variables that should be taken into account and often are the main issues when tweaking things more efficiently.

More is better extends mainly into Lighting, rather than nutrients which seem secondary to me for folks in the USA, that's where many have run into problems IMO/IME. Not enough CO2 and too much lighting.

But my response is to deal with people wanting high light systems and driving this vicious circle of nutrient uptake at progressively higher rates.
There is a lot to be learned down that road that can later be used for lower lighting systems, but generally 2/w gal is great for the new person I suggest they start there and learn how to keep good CO2 first.

But they cannot help themselves and go out and buy 4w/gal powercompact systems and don't listen.

Even at 1.5-2w/gal, you can have excellent growth and have very low NO3/PO4 levels, with a good fish load, perhaps not even any NO3/PO4 dosing except at weekly water changes etc.

Worked jim dandy for me anyway. You hardly clean the glass ever. Each herbivore is that much more effective per critter also. If you neglect, and we all do at some point, things are more stable, electric cost less etc.

Claus also has done a fair amount this and I can back his comments up with more references he did not include from folks I know personally that have worked on CO2 and light.

I think lighting excesses should be addressed personally. But folks seem to believe they must have high light to grow plants, this is simply untrue.

Jeff grew nice looking Gloss at 1.5w/gal, Steve and Jeff both did at 2.1 w of mainly NO FL's at 24" deep tank. Every one saw it.
I grew hairgrass at 1.6 w/gal, pearl grass at 1 w/gal etc.

Regards,
Tom Barr
 

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Discussion Starter · #13 ·
I am in definate about the importance of CO2 and the sometimes overdone use of high light. I, being so very new to this hobby, have experienced many of the blunders and issues resulting from hasty decisions and lack of "proper" research. For what it is worth, let me give a couple of my own examples:)

My first, amin tank, is my 10 gallon with CO2(on week of pressurized, weeehooooo)and 45 watts of NO florescent. From the begining, as I got into plants I would make constant changes trying to improve my plant growth. All in one ferts from various manufactures did not seem to make much of a difference. I added DIY CO2 and incresed the lighting to 30watts NO florescent. Plants pearled and began to grow much better. At hte same time I read the Sear/Collins stuff, PMDD info and ordered some chemicals. KNO3 and K2SO4. I decided to not mess wiht P because it caused algae, right. THis of course was an error on my part, remember I said I often am hasty and don't learn enough first:) Well I dosed to N10ppm, K 20ppm nad the occasional dose of Sere Florena. Good growth at first, which I now attribute to the N and CO2 and then it started to go south. I read and learned more :wink: added more Sera and upped my lighting to 45 watts. I built my "pressurized" DIY CO2 system to maintain my CO2 levels in the 30's(it worked perfectly, BTW). Better growth the nothing. I realized that I had been eranous in my thinking about P and the need for a trace suplement. More stupidity on my part:) I ordered Floruish, bought Fleet for P, got a test kit (that does not work and the reason that I started this thread in the first place). Started dosing flourish adn P. Thnks to tsunami for htat help :wink: ANd now everyhting seem to be growing great. THis has been going on for about 3-4 weks now and I only continue to see improvement. Is this a bit labor intensive, yes but I like that actually.

So in the end here is what I got, I do a 50% wc each week. I dose 5ppm of N, 10 ppm k, 1.5ppm P, 2 ml Flourish and 1 ml flourish Fe at the wc. I dose 1ml Flourish and Fe every day, keep my CO2 levels in the 30's and watch my plants. Mid week I test if I think I am low in anything and then dose accordingly. Mostly now, I watch my plants and algae. They usually tell me when they are running low on something. Also, I will now that the N and P I am running lean, but I wanted the colors from my plants for photography reasons. Now that that is past I will increase my N to 10 adn keep my P dosing at 1.5-2 each week. Test at wc to make sure there is no build up and continue to try and research and learn, learn, learn. I might even remove a bulb so things slow down, but I doubt it:) I thnk the upgrade to real press. CO2 will be a real nice timesaver. I don't mind the half hour to hour I spend working in this tank each week. Its a hobby and I enjoy it. I spend way more than that looking at it:)

So the long and short of all of this is that I agree with both of you, Tom and Jeff, entirely and I am very glad to discuss this. I am always happy to try and learn more and I know you are all very knowledgable and intelligent. I regret that I did not spend more time learning before I started but actually thats the way I work so it may have been better this way in the end. I am gad I did not know to much in the begining or I would have started with way to much light and not enough knowledge and everything would have gone to hell:)

Anyway, I digress.

Thanks:)
 

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Back to the orginal question.
Rates of .2-.3 ppm of PO4 (SRP) appear to be removed per day in high light CO2 enriched fully planted tanks. I did this a dozen or more times as controlled as I could.

This a _sustained_ rate. More biomass of plants, plant species etc may make this rate different.
This is at max uptake but this does NOT imply that max uptake = max growth rates with PO4, plants certainly take up more than they need.

Plant tanks might take up more, I've heard of .6ppm being removed a day, but small amounts to a limited tank are often removed in hours(say .2ppm added to a limited tank can be removed in a few hours time)

So full circle and away from the fruitful digressions.

Regards,
Tom Barr
 

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Discussion Starter · #15 ·
First, before i forget.

Error, there are 2 kinds of P available to plants SRP-soluble reactive phosphorus, and DOP-dissolved organic phosphorus. The SRP is the kind we add to our tanks by dosing fleet or KH2PO4, ect. DOP is from plant and animal waste breakdown, fish fooed, anything organic in nature. This, I have learned from Tom Barr's article here, which I found to be very informative and helpful.

plantbrain, thanks for breaking it down to simple terms :wink: I guess what I was noticing was not unusaul, especially for plants that had been P limited, probably fo months. I am finding now, that I have definately seen a reduction in my dosing from the beginning of this thread and now I only dose it once or twice a week:)

Thanks everyone. [/url]
 

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plantbrain said:
Back to the orginal question.
Rates of .2-.3 ppm of PO4 (SRP) appear to be removed per day in high light CO2 enriched fully planted tanks...

This a _sustained_ rate. More biomass of plants, plant species etc may make this rate different...

So full circle and away from the fruitful digressions.
Tom,

Question is, do P uptake rates change as plant tissues become more "fat" with stored P? Or inversely, does a particular mass of plants suck down P faster when starved for P?

I think your seminar on PO4 mitigation may be misleading you about P uptake. If plants are effective at removing combined P from both SRP and DOP down to .015 ppm and they are less effective at removing DOP, then one can conclude, that the remaining .015 ppm would be primarily DOP. If this is true, perhaps your new emphasis on SRP, while theoretically supportable, may not be applicable to our practice. We have a long history of observing how plants grow quite well with P derived only from fish waste and organic decomposition and your new SRP favoring premise ignores this history. Since algae has an advantage of only .005 ppm combined P and this exceeds testing's margin for error, you may be giving this study more weight than it deserves.

My observations suggest that uptake of N slows as reserves of P decrease. So perhaps plants may ration out P as it becomes limiting; or if we apply converse logic, plants may use P with extravagant gusto when P is abundant. My general conclusion is that sustained measurable P in aquarium water encourages maximum N uptake which eventually results in N exhaustion if N is not replaced at faster rates.

P and N seem to be linked in their ability to determine rates of vegetative growth. In the P dominant model, here widely recommended, growth is maximized and plant color is reduced to an even green. In these systems it has been observed that careful reduction of N has provided improved color. However this proves difficult because in maintaining P concentrations the rates of N uptake remain maximized and the practice flirts with N crashes.

What I surmise actually brings color to these plants is not a low N to P ratio, as some claim, but a change in the ratio of N forms used. Since in most aquarist's supplementation routines, N comes solely from KNO3 while ammonium is derived entirely from biological momentum, we can conclude that biological momentum determines ammonium production regardless of how much KNO3 is introduced into a tank. Since ammonium preference is widely accepted I conclude that higher P forces plants to take up more NO3 because ammonium is taken up at its rate of production. This is why I suppose that color reflects the ratio of N forms used.

Over all my premise is that P reserves function as the accelerator pedal of our enclosed biological mechanisms while the ratio of N forms are governed by rates of natural ammonium production. Controlling phosphate reserves (not maximizing them) will provide an aquarist with the means to regulate a tanks momentum and the forms of Nitrogen assimilated in a tank.

Jeff
 

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I'm not sure about whether the plant's uptake is faster if "starved vs "fat".
It could go either way. My statement of rates is based on what I would consider "fat". Specific plant species may indeed have different rates, but are they that different?

I think this would play a role when you limit a certain nutrient down to the bone. While as a general method, this might not be a good idea(say with species that do not care for low PO4 levels), but for finding tolerances for specific species, this is a good method.

DOP vs SRP is well studied in natural systems. Our kits measure Total PO4. Submersed macrophytes can remove down to 20-50 ppb(not million) but not beyond this range of total PO4.
The study is very well done, I know those involved and have review their work and given feedback. South Florida water management district has the lowest PO4 mandate of any place anywhere I know of. They need water treated to 10ppb. Few things are capable of doing that on large scale. They have considered many options and researched this issues with many millions, many researchers.

DOP can be broken down, and this process is slower and more difficult to measure since as it's brojken down from DOP to SRP by bacterial reminerlization, it's consumed by algae, plants, bacteria etc and rapidly turned into Organically bound PO4 once again.

Much like how much NH4 from fish waste are the plants getting vs the NO3 from KNO3 etc, the same can be said for reminerlized waste from fish for many nutrients including how much CO2 is coming from bacterial respiration etc.

A lower light, higher fish loads, this will play an incresingly large role. So will reminerlizational processes. At lower light, these processes have the time for the bacterial cycling to occur, at higher light, there is not enough time without destablizing the system. This can be delat with by adding NO3, KH2PO4 etc.

You can answer the question, but you need to test both forms of PO4. I know of several ways at getting at this but it's a lot of work I certainly do not plan on doing anytime soon:)
Theory and natural systems are all we have really to work with. I'm fine with that as long as the studies are about algae, temps in the right range, have plants also, good research.

Yes, N uptake certainly slows as the PO4 drops/limits, this is a cascade effect and the plant becomes co limited.

This is very common with respect to CO2 and NO3 or PO4. Yes, your conclusion is correct about PO4 excess causing NO3/NH4 to be driven down.

But there's going to always be one or more nutrients that will be driven down, be it PO4 or NO3, etc, pick your poison:)
You still need some source of nutrient supplementation.
But using less light to drive this will reduce the rates of uptake and allow more wiggle room with your chosen method.

If you are a purist, non CO2 tanks are great, no KNO3, CO2, Traces, water changes etc. I have a great tank with this method. I would say it looks better than many CO2 tanks. It also takes longer.

I'm not a big fan of NO3 limitation for color although it will bring the red out of many plants. I've been the King of NO3 crashes, I'm sure a few other folks can attest to this issue for their own tank observations.


As far as the forms of N, I think you have some credence for sure there, I suggested that a few years back on the APD. I'd suggested to have the best color, even certain plant will do better with more fish etc, more reliance on NH4 is needed from a fish waste source.

But why then would a non CO2 tank not have better color than a CO2 enriched tank since the reliance is almost exclusively based on NH4 waste?
Would a lower light tank produce better color also(CO2 enriched)? Since it would allow more NH4 to be removed and less NO3 for it's N needs??

Which observations do want to you consider? I think there are arguements for both sides of this coin.

Still, I feel is correct that better health/color/growth occurs with a higher relative % coming from NH4 than NO3. But this is a tricky thing since it means balance and many folks know NH4 is playing with fire.

I'm not sure it's worth it for most plant folks. Live with some green and have a nice tank or try lowering the light and relying on the fish more.
Many folks are roasting these tanks at 3-5w/gal with PC lighting.

I'd have a tough time quantifying this, but it seems to be true from my perspective/observations.
It also allows you more wiggle room if you forget/neglect the tank and we all do it sometime or another. Not a bad idea generally.

This might be why Amano's plants look pretty good since he adds lots of shrimps(waste) to the tanks, no algae and lots of NH4. It certainly adds a lot more NH4 to a system even if you do not consider their algae eating abilty and simply consider plant growth/color alone.

Still, I've had excellent results with few fish/critters in tanks with good dosing habits. I'd have a tough time showing real differences IME/IMO.
But part of me would like to argue in favor of more fish waste:) It is good if you are forgetful.

Take Bob's Gratiola(Limnophila aromatica) for example.
My tank has no fish, just snails and my plants are much redder than his plants and smaller/not as green, so this seems to counter the whole premise, but this is one plant, but there are others like his L repens. Mine are many shades redder yet my biload is dramtically polar opposite of his, yet the health, color etc is much better, the light is also higher.

So the observations I've seen and experienced are different than what I've just argued for:) At least for these two red color variable plants. My GH and KH are 5 and 3. PO4 is very high as is my NO3/traces etc.

Looking at plants and ignoring the algae is a critical observation.

I've said many times, as the lighting intensity increases, so does the tank's reliance on inorganic sources, be them CO2, NO3, PO4, Traces, etc in order to keep the balance.

I'm not sure that fish loads are really that significant in health/color etc as you and I have suggested, more important perhaps is simply not running out of anything for long at a given rate. NO3 vs NH4 etc my be less important in practice.
I could argue both sides of this coin.

Regards,
Tom Barr
 

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plantbrain said:
Take Bob's Gratiola(Limnophila aromatica) for example.
My tank has no fish, just snails and my plants are much redder than his plants and smaller/not as green, so this seems to counter the whole premise, but this is one plant, but there are others like his L repens. Mine are many shades redder yet my biload is dramtically polar opposite of his, yet the health, color etc is much better, the light is also higher.
Tom,

I am guessing you refer to Bob Adler here?

Bob's exact husbandry practice remains a mystery to me but ill try to relay what I thought was happening. You will see it supports my "color" premise, if he was following my prescription. We do know he employed the mechanical changes and was pleased with his results.

When I talked to him I got the impression that he was finishing his weeks with P gain and N loss. After a water change he was adding more P to produce 1 ppm as Tom had instructed him to. At that time he was experiencing only green colors and having trouble maintaining 10+ ppm CO2. I suggested he eliminate his wet-dry bioball filtration and reduce his overflow fall in an effort to increase available ammonium while decreasing CO2 loss. You made a great addition in your suggestion that he replace the wet-dry with a micron filter bag! Like you, I could't begin to imagine his fish load.

I think he was following my advice to add KNO3 but not P in an effort to produce a falling P and more stable N measurements. From what I saw, he wasn't getting the strong pearling that I associate with a good CO2 concentrations. It is concievable that he was not producing vegetative N uptake at rates needed to out compete bacterial ammonium conversion. Its hard to tell, Bob was getting information from you, Alan and myself and probably synthesized his own idiosyncratic method.

Gratiola and L. repens seem to be good plants to observe color in tho'. It was the plant Eric grew to match the color of R. roundifololia "green" in what I believe was a classic P dominant tank.

Andrew visited my tank a few days back and I cranked the light timer forward to accomodate his visit. Of course my plants were trying to fall asleep with the lights on. As my Gratiola closed up tighter and tighter the undersides of the leaves began to change from a pink blush to a striking purple. It made me wonder if it changed like that every night or if it was just part of tucking its head under the pillow. The next day all my plants slept in and got a very slow starts. Its kind'a miraculous to notice that plants have a sense of time.

Jeff
 

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Stable N, I think that's what really may be an issue here.

This can be achieved through rigorous dosing, less lighting, bio fish/critter loads, dosing less PO4 etc.

I think there are many ways to skin this cat, but which of these are most suitable for the grower? Generally less lighting, most folks want fish/critters, most are slackers about dosing at least at some point.

Bob's methods are rather an amalgam, but he was taking my advice about the dosing the last 2 weeks but I soon realized how much fish load he had. Alan had warned me about that. I soon cut the KNO3 by 1/2.

The micron filter bag idea I used some years back and it's really and big help, anything that removes the finer particles is a good thing IME with planted tanks.
They are easy to clean and last longer and can over flow when clogged into the sump.
Berlin style reef sumps have this set up also.

Bob's tank might have been a hit/miss thing because of the timing, but the color on those two plant species should have changed in the time period, I've seen this when I've changed KNO3 dosing routines and fish load additions with these plants.

I have L repens in a heavier fish load tank and still have the same color health etc. I use canister filters on all my tanks and they get cleaned perhaps once every 3-6 months. So wet/dry NH4=> NO3 conversions are not that large of an influence on either tank.

But back to stable N. N is such a critical nutrient and is with CO2 as far as one of those things people louse up when they get algae.
NO3/NH4 and CO2 are the main issues folks have with keeping plants.

It takes awhile for plants to recover from N stunting, some are fast at recovery, some slow.

A very good plant to see this is Mic umbrosum. It's a fast at recovery and very sensitive to low NO3 and to a lesser degree NH4.
Ammannia seems to be (much)slower to recover from N deficiency.

I drove NO3 levels to 75ppm in the past for several weeks. I found no algae response when the other parameters were good but I was not adding as much PO4 at the time.

I have been re evaluating high PO4/NO3 lately and truthfully I've been happy with 20ppm of NO3, I think folks over all have trouble with their test kits for PO4 and for NO3.

Testing how much NH4 the plants are getting is impossible without using isotopes ince it's used up before it's able to be measured.
I was going to inject some N15 in the form of NO3 into a culture with plants and with algae and see who got what.
Then I was going to do the same with N15 and NH4. But the Mass spect is too sensitive for enrichment studies really here and I'd have to use another one that is backed up for the next 7 months with other folks using it. But the question could be answered and you could do a number of studies comparing the two plants grown in different NH4/NO3 ratios etc.

Plant species certainly seem to respond differently to these sources of N and ratios of P. But is this an issue of the status and needs or is it simply some other variable like not enough of something else?
Keeping one single dependent variable from being corrupted is tough.
It either takes a lot of time and work, or you guess with experience or you look into the data/research etc and perhaps mix some of all three of these approaches.

Using P04 to stablize N is not a bad idea, plants respond much better to PO4 limitation than they do N limitation!
As long as the PO4 is not too low, this works well and was the basic premise I think of most Europeans from years past.

But I think it does not help or deter algae, but if you look at plant health, there are a number of ways to stabilize N levels.

Increasing the ratio of NH4 the plants get has it's limits.
Whether from inorganic or organic sources, I've been down this road a few times. It's fire at higher levels.

Still, I'd rather have NO3 and less chance of algae, than the little added benefit for NH4. For most folks, keeping stable well dosed tanks is quite the challenge. If something goes bad, they will have worse algae this way, NH4 is much more likely to cause algae than higher PO4.

Although I'll agree that NH4 is a good thing when dosed from the fish load, I'm not sure it's that critical in better plant health, research has showed it increases growth rates in some plants(certainly not all 300 species we like to grow) but this does not impy health and color in any form of quantification. What are the units for coloration in leaves? Nanometers? What;s the best color? What's the best health status/growth form?

You and I might have an easier time balancing a tank, but explaining that to some one without experience with the fish/plant balance can be tough. In person is much easier but on the web it's very tough. I tend to opt for the KNO3 dosing but I may increase the levels since many bottom out their NO3.

I'd figure that 30ppm of NO3 a week is pretty high for NO3 consumption.
I need to do a non substrate growth or an aerobic substrate(RFUG) to make sure there's less denitrification occuring, there are other methods I could use to measure denitrication but the 30ppm a week seems pretty high.

If I add 60ppm a week, then I do not believe the tank could ever be limited.

Okay enough for now.

Regards,
Tom Barr
 

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Discussion Starter · #20 ·
See Dennis,
see Dennis feeling dumb,
See Dennis getting smarter :)

I am reaching htat point where I should probably start lurking wiht this. I certainly don't have the background and experience you both do, although I am starting to learn. I really like that. Thanks. One of hte wonderful things about these forums is that you can run across very intelligent descussions like this one. Its nice to hear two people discuss something they know a lot about. Keep it up:) for my sake.

Can you(either of you) explain better to me the relationship betwen N/P. Something like P causes plant cell x to increase in size thus.......and in what way do they affect color. I realize this is a very broad question since all plants are different. Do certain nutrients (or lack of) cause higher production of the various chloroplasts in the plants' cells. If I understand correctly, certain compounds and elements affect the stoma cells of the plants, regulating what and how much of other things come in and out of the cell membranes(I could be completely wrong wiht thatm sorry if I am). AN example of this would be the Mg:Ca ratio that there was some discussion on a while back. Am I think of this correctly.

Jeff, your NH4 theory makes some sense to me because, to my thinking, NH4 is one of the first forms of N avaliable to plants in nature. It seems logical that they then would have evolved to prefer that source. How this affects the color is beyonfd me at this point though. One question then that I wonder is why then do plants prefer SRP over DOP as plantbrain stated. IS not the DOP more organic and there for the more common form in nature? Or am I just thinking about this all wrong.

There are many htings that I accept adn sort of understand without knowing why. One of these is that plants can outcompete algae for nutrients. How? If perphyton (algae right?) can uptake a nutreint like P down to the .5ppB range then how could the marcophytes have the first dibs. Wouldn't what is avaliable to one be avaliable to another. I know Tom Barr said they actually live in different enviroments, and I believe you, but how could the plants out compete something living on their leaves?

So much more to learn but i just got home from worka nd my brain quits:)

Thanks
 
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