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Discussion Starter · #1 ·
Hi all,
I got bit hard by the plant bug about a year ago after not having an aquarium since I was a kid. Even after trying several different methods, I could never quite win the battle with algae. I decided to make up my own method. I have tested my water and it has the following specs:
TDS: 35ppm
KH: 30ppm
pH: 6.1
CO2: 35-40ppm
PO4: 0ppm
NO3: 0ppm

So, clearly the plants have to get their nutrients from the substrate. I was reluctant to use soil because my feeling is that dissolved organics (DOP and DON) are algae's nutrient source. Instead, I am using a "nutrient plenum" which I read about in the archives on to provide trace elements and positive cations.

I basically set up a 0.5" thick cavity under a substrate of flourite+profile. The plenum has two thin tubes feeding it. I inject Flourish into the plenum and it is allowed to diffuse slowly through the substrate. To prevent diffusion into the water column, heavy ground cover is good. Of course, until the ground cover is established, injecting nutrients should be done judiciously (i.e., not put too much in). I initially put a foam layer between the gravel and the plenum, but I found that very little was diffusing from the plenum into the substrate.

For macros, I am using quite a few Jobes plant sticks buried under the plants. I have not had any trouble with leaching into the water column.
I will try to post some pics, but I can't seem to get them to show up at the moment. Let me know what y'all think.

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What types of test kits are you using.
Have you run them against known standards?

Algae is not limited via the water column. The waste from the fish and plant decay alone will solve that.
A Plenum is a waste of space IMO.
There is flux out of the substrate also, it's occuring.

I think you will find over time and after a few plantings, you might not like the jobes. But adding PO4/NO3 is not an issue as far as algae is concerned. If you had algae issues in the past, it was not from having those present, it's generally from not enough NO3/PO4/CO2.

Tom Barr

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Discussion Starter · #3 ·
I know that some phosphate and NH4/NO3 will come from fish waste and feeding. However, I do about a 40% water change everyday (my tank is small so this is very easy). Plus, my fish population is not that large -7 tetras and one small SAE. I feel fairly confident that my PO4 and Nitrate levels are close to zero.

Regarding the plenum, it's not really a plenum that's used typically in reefs. I mean, that it's not meant for denitrification. It's just a means to dose nutrients through the substrate first. My fluorite is pretty much covered with plants like the glosso, so not much escapes throught the water column. I have tested with a TDS meter before and after dosing to verify this.

Anyhow, I don't think denitrification is that bad, because deep substrate denitrification means ammonia which plants prefer and it is isolated from algae in the water column.

Oh, sorry about the photo I will resize the next ones I put up. Is there a way to edit previous postings?

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Well with 40% daily changes I think you will probably never test much in the water regardless of how much is coming out of the substrate. I think that may be the key to this tank, if you wait a week between water changes I'm sure test results would be different and problems tied to the extra rich substrate may occur. Plus, by changing water so often I think you are somewhat simulating what occurs in nature, that is constantly flowing water that is poor in nutrients however never depleted because of the constant flow of new water. We use higher levels because the water is the same for a week and we don't want it to become depleted, if you change it daily the nutrient levels required are probably barely readable by most of our test kits.

Wish I had the will power to do daily water changes :)

Giancarlo Podio

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Discussion Starter · #5 ·
Well, the point with the daily water changes is the fact that plants can grow with an extra lean water column. My goal was to basically make it impossible for algae to grow. Also, my substrate is not rich, except for the Jobes sticks.

I think if l left it for a week, there would not be significant leakage from the substrate. I do the water changes to remove organics produced by the fish and the feeding, and maybe the plants. I can tell there are organics being produced because of the surface scum. Surface scum is not present when the water is really clean.

When I progress to a larger tank, obviously the 40% water changes will not be possible. In that case, I will probably have to employ chemical means to keep the water pure, i.e., a lot of activated carbon, ozone, and/or a protein skimmer. I like gadgets so the more the better :D.

Is it possible for the moderator to delete my 2nd post, because the picture is too large and it makes it hard to read. The image hosting website that I put it on does not allow for easy deletion. Thanks.

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Thats pretty good looking Rotala macranda green (Right???). Its a cool idea. I want to try something like that out on my 20 gallon. But i think plantbrains advice is real good. A lot of people follow it and get good results.

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The plants on the picture look very healthy (with the exception of the unusual white spots on the Lobelia). Clearly you are doing something right.

Yes, Tom's advice is used by many, but there are other good ways to run a tank and your tank is another proof for that. To me the "best" way to run a tank is the one that requires less work. Your daily water changes would be a burden if you try them in a bigger tank.

But I think that what you have done makes a good point about the importance of water purity.

May be I missed it somehow but did you have any algae problems at any point of the development of that plenum tank or not?


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40% daily water change with what kind or water?Tap or RO or?

Most tap has some NO3, some has PO4 like my old tap water here in Marin.

The dutch did large frequent water changes and had high NO3/PO4 in their tap. Many places have this.

The issue for me is the moss, it does not have roots. So it's getting enough nutrients.

And if it's able to grow, so is algae.

I've found algae in places where we could not measure any NO3 or PO4.
I just do not buy folks saying algae can be limited while the plants are not.
I've never found evidence of this in the research either and I have looked.

Algae phyisology just does not work that way.
Plants will grow in those same places also, but the substrate is the source.

Many waters have a pH of 5 and no measurable hardness/nutrient levels.

The other issue is that the nutrients are often used up as fast as they leech so you really do NOT know how much of the jobes is going into the water column or is available for either plant of algae.

Plants also leak a fairly substantial amount of nutrients.

Both Tropica and Amano have done small tanks like this with no substrate and water column dosing and daily changes.

If you are going to go to the effort of a daily water change, dosing is not hassle.

As far as elements causing algae, this is fairly clear.

But I will challenge you to show evidence that you can limit algae by nutrient limitation to the water column and still have healthy plant growth.

I can clearly grow plants with zero algae with high nutrients, so does the nutrient levels in the water help?


You seem to assume that they do.
That was my point.

We can find many examples I nature of this situation, but it does mean it's preferred by the plants nor limits algae in any way.

That is a dangerous assumption.

Plants have a source of nutrients, whether from the substrate or the water column, they will do well.

You will get higher growth rates, thus preference with the water column.

It's not an issue of MY method vs a substrate method, that has nothing to do with it. I'm making a point you gain nothing by doing such a method dealing with algae.

If you dosed back the KNO3/KH2PO4 and did daily water changes etc, the plants would grow great also without any substrate and there'd be no algae. I've done that also for close to 10 years. I also tried the rich substrate approach, we have archives and archives of this on the APD, we went around and around with it there.

This is nothing new.
Not sure why people think it is, sort of ironic.

I did that substrate water column clean method also.
One thing that helps the water column clean method today is huge water changes and higher CO2 than in the past.

This seems to have a negative effect on the algae spores(water changes) relative to the larger plants which can take the shock better.

It's not so much the method, it's the large water changes daily.
Using TDS is not necessarily going to tell you your NO3 level at all.

If you are using CO2 and have that measurement, then you must have a KH and therefore some TDS, likewise for GH to some degree.

Try adding a small amount of a stock solution of KNO3 to see.

The small trace amounts of PO4/NO3 in the tap water are not going to show up. Unless you are using reconsituted RO etc and have measured the tap with a good quality NO3 kits, it could very well be the case.

Folks use to say I had "magic tap water".
There's no magic and because I am being critical and looking into this question it does not mean I am being anything more than that.

These are valid issues that sometimes cannot be addressed directly so finding other ways to solve the problem or question is sometimes needed.

I'm not partial to a method, I'm partial to an understanding without so many assumptions.

This is how you figure stuff out.

That's the goal, merely saying there is another way than my so called way(which I there are many ways that I do and have done things including this one... ahem) is not going to solve or help better understand things.

Methods need to be looked at critically, not just bashing the critics or another method, that behavior is politics, not science.

A cat can only be skinned a few different basic ways, but there is more than one:)

Tom Barr

Tom Barr

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Discussion Starter · #9 ·
I hope that I did not come off in any way as bashing your's
or any one else's method. The amount of knowledge you have
contributed to the aquatic gardening "hobby" is incredible and
immensely useful. I read all of your posts with great interest.

The way I am thinking is phosphate and nitrate cannot just
be limited, they have to be zero or as close as possible. I know
zero is physically not realizable just because of feeding, plant
leaves decaying, etc.

I think it was in your post that I read a while ago about algae not
being limited until phosphate was in the PPB range. I think this
is true. Foliar uptake should be able to easily handle this level
between water changes.

Same goes with nitrate, IMO.

I'm an engineer and hella anal-ytical :lol:. It doesn't make sense
to me how you can add PO4, NO3, K+, etc. into the water and not
expect to see algae. I have seen TV shows (I know don't trust TV)
on PBS that maintain PO4 and NO3 are metrics for pollution/algae
growth. What about the more mature reef sector that will do
anything to avoid PO4? Reefers strive for 0ppm PO4.

If you look at my moss, you can see that it is struggling. This is
a weakness of having a lean water column plus being under bright
lights. However, moss doesn't need that many nutrients to grow;
it can get it from the wood, just like real moss does in nature.

Let me know what you think.

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Discussion Starter · #10 ·
Resize Pictures

Here are the resized pics. I don't why they look so dim, I have 6wpg of NO. Is it possible for the previous photo to be deleted or my double post? Thanks.

Plenum Closeup

Corner(shown previously, but resized)

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2,072 Posts
I get along with engineers and understand them because I almost became one. I often get into debates over the biological aspects in aquatic ecosystems with them.

I am not addressing you or anyone in particular, I think many newer folks do not know my history using substrates and the other folks in the past. It was the method way back when. I did a lot of work on substrate back in the 1980's and 1990's.

Some have said that the water method is old hat, that rich substrates are the all the rage today, heck, most simply do not have access to KNO3, but jobes, boiling(which removes the NH4/Urea) worm castings, manure, chicken crap etc all have the same elements and uses for plants. These have been used since at least the 1960's in planted tanks. I can assure folks, this ain't new.

What I am pointing out is that the water column does not need to be limited, this was/is a myth. That is new in the plant tank hobby.

It's not new in research though, PO4 and NO3 are used as eutrophic indicators to some degree, but when you add plants in a shallow lake, even with high PO4/NO3, if there is roughly 30-50% or more substrate coverage by plants, the water will be gin clear, if you removce the plants, the lake will turn to pea soup.

Most studies looked at northern lakes, since most researchers tended to be bais to their location of institutions rather than tropical or subtropical lakes that do not freeze and have stable long term plant populations.

Other assumptions like taking into account the amount PO4 locked up in the plants when testing the water column were also not taken into account, see Phillips 1978, which did not adress that, but used the water samples that had the algae's PO4 taken into account.

Suddenly there is no pattern that relates algae to eutrophic waters, eg an R^2 value of .10 when you sample the PO4 in the plants, vs an R^2 value
of close .82 without that critical piece of sampling information.

The paper was bias towards the algae. It's been cited some 300+ times also, so it's gotten all around, but many lakes don't have plants or only a very few around the edges in the littoral zones, so then the papers are generally correct.

Few look at plants vs algae. They mainly look at algae, so there's that bias as well. There has been far more research done on algae than aquatic plants also, so there's even more bias in the literature.
Additionally, emergent plants do not have the same issues as submersed plants and many wetland plants are emergents, so there's even more bias.

So these are few reasons why folks say the NO3 and PO4 cause algae in a planted tank.

Back to the substrate:

If worms is all ya got, you have to work with it. If you have more materials to test with and try out, then you can compare the two.
You can force any method as long as there is a supply of nutrients for the plants for a given rate. But over time folks settle into a routine that works for them. I hope you plan to take a vacation some day and can leave the tank for a little while:)

Thanks for the overview of the tank, looks nice.
An aquascaping notion: You might try extending the log upwards at angle and try and cultivate the moss on the wood more and keep it trimmed down low but not remove any that spreads as it attaches to the wood.

Wood is extremely non labile as far as nutrients good. Moss is not going to derive anything in an aquatic environment from the wood realitsically.
You'll find moss mainly growing on rocks and stable substrates(sometimes logs but this is more rare unless they are very large or along the banks on living or dead stumps), not wood preferencially.

Moss will be found in generally cooler waters rich in CO2/GH.

The moss does not look like it should really but is growing. Moss will "ball out" when it is growing well and has been in a good environment for awhile(several weeks). How old is the tank?

I think a bit later you will want to try and experiement with dose KNO3/KH2PO4 vs jobes.

But you can continue the method since a tear down and redoing the substrate would not be tough.

The other thing you can do, add the jobs to the plenum, that's what I would do personally.

This would prevent uprooting..........ahhhh......
It would keep that nutrient rich layer away from disturbances and still provide some exchange.

The jobes generally will be fine..........until you uproot, but I know the key element here why they are NOT presenting an algae bloom, even if you uproot, you do daily water changes so the NH4, not the NO3/PO4 etc is being removed before it has a chance to induce the algae spores which are certainly there and present.

The inducement takes about 30 hours on average with NH4 present in the water column. The levels are very low for NH4.

When people do large prunings, I always suggest they clean the filter/prune first, net out any 3excess mulm/dead plant leaves etc.

Then do a large water change.

You can dose back the nutrients to the water column or leave them in the substrate, either way the plants will have access to them.

But since you are doing the large daily water changes, something few people would be willing to do and you might not want to keep up after a few months/weeks/years, you can get away with little to no effect of the NH4.

I think you would be very hard pressed to show a preference in a tank for NH4 over NO3, in control cases with some plants, this is true, but most Ag crops prefer NO3 over NH4. Rice, a wetland plant is the one exception.

If you did weekly water changes, say 50-60% etc, I think you might find some algae creeping in here and there.

If you did a replant, then no water change, I'd bet a nickle you'd get an algae bloom.

If you added some KH2PO4, say 1ppm, I'd bet you would not get an algae bloom.

But that would drive the N uptake higher.

Fish food is higher relative to the plant's needs in N, so fish food will generally limit the PO4 in a tank if that's your only input.

The issue I'm trying to suggest here mainly is one of control and dosing.
While substrates do and can work and we generally all use them to some rleative amount, dosing the water column is generally an easier more stable method.

It requires more consistancy than substrate dosing but prevents issues from occuring and you can test and know what's in your water vs guessing what's left in the substrate after a few months.

Our habits are very much at play when gauging a method.

A non CO2 tank is very easy and nice and relies on the substrate, but the uptake rate from the substrate is limited by light and CO2.

The loading rate(fish waste/water change inputs/plant decay/leeching) and uptake rate of the plants are the elements that need balanced.

It's a fairly easy 2 box model.

All in all, you might want to see about a simplfied method of water changes or automate a small float switch and timer set up for slow water changes at night, with a carbon prefilter for Cl removal.

The other thing I'd suggest you try, after 6 months etc or when you need to re enrich the substrate, try adding the sticks to the plenum layer, actually you can do this with that down spout you use for dosing the traces so you might not need to remove it.

Adding the traces there I do not think will do much either way. You can try this and see for your self.

You can also try adding the KNO3 or KH2PO4 to the water column as well.

You need not worry, you will reset the tank when? Tomorrow?

So the tank will be re set each day..........

So you can experiement around.

Just don't get too many jobes sticks floating around in there.

You'll be dealing with green water then. A UV might help you later if this occurs.

So there's some thoughts to go after and try out here.

I'm not suggesting to you to change your method here, just try some things out to prove to yourself what is really going on.
Each method has something to teach you.

This will help you become a better grower and know why algae was an issue in the past.

It's not a big deal really, it's a small tank and can be reworked if you make a mistake, but try to be careful when you experiement.
Ultimately, I think you will tire of daily water changes though, so I will suggest that change:)

Tom Barr

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Discussion Starter · #15 ·
Take down the gigantic photo!!!

I can't take the picture down, because I can't access the picture on the image hosting site I am using. If someone could take it down, I would be grateful. I will post a resized image then. Thanks.

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Discussion Starter · #18 ·
I think there are two types of denitrification: assimilatory and dissimilatory, resulting in either NH4 or N2. It depends on how oxygen deprived the area is. Assimilatory takes place under anaerobic (as opposed to anoxic) conditions. Anyway, I don't know that much about denitrification and this is not the aim of the so-called plenum, anyhow.

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Mc Finn, give those ideas a whirl and see. It's a small tank and not too hard to whip back into shape.

I would like you to see the results for yourself.

You are not going to get any significant NH4 production via the NO3=> NH4 pathway in a plant tank substrate. We labeled N15 as NO3 in a 1 meter cube wetland in the soils lab, I think it was 0.0401%(or close) of the NO3 was converted and the substrate was mighty rich in OM and about 40cm deep.

It might be significant on a global scale or when you are talking about 10000 hectacres etc but not in our tanks:)

Tom Barr

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Discussion Starter · #20 ·
Yeah, I guess NH4 from NO3 production ain't gonna happen in our tank substrates. Anyway, that is some cool stuff that you get experiment with.

I will try some of your suggestions just to experiment with. Some like the automatic, continuous water change will not work because I live in a tiny apartment with roommates who would not stand to see tubing running from the common bathroom to my room :lol: . I will definitely be adding the Jobes to the plenum next time around.

Regarding the KH2PO4: I don't really think that PO4 in and of itself causes algae. I know, I am sort of backtracking on what I said. So, if I add KH2PO4 at every water change so that my concentration is initially 1ppm, I don't think it will cause algae. There I said it. However, I am not so certain that if I stop the daily water changes and still add PO4 daily that I will not see algae.

The problem is I can see buildup of surface scum in my tank if I don't do the water changes for a few days. This I think indicates organic build-up. DOP and DON are what I am afraid of. Adding the inorganic PO4 will make things worse, maybe. I am not sure.

When I first started my tank, I did this: weekly water changes + water column dosing (both macro and traces). This made my existing algae problem worse.

If you had a bowl full of algae, and added PO4 and KNO3 daily (to say 1ppm of each), I would bet that the algae would grow faster than without the nutrients.

I guess what you are saying is that adding the macros won't significantly increase algae growth because these concentrations are far in excess of what the algae needs anyway. That is a good point. The plants, on the other hand, will suffer with low concentrations of nutrients. Don't kill the patient while treating the disease.

I understand that dosing the water column will work for most people, because the plants are nutrient deficient. But, I think that you are basically just tweaking the plant growth/ algae growth ratio. Basically, the plant growth is increased relative to algae.

If algae growth is decreased, how? I can only think of two possibilities. (1)Algae are missing a nutrient needed to grow, that maybe the plants used up. 2)Allelopathy. I don't really believe (2).

Sorry about the long and disjointed post. Just thinking aloud.
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