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The golden question:
I got into a discussion with an individual a while ago about algae control. We tossed a bunch of ideas back and forth. We agreed on a few points and disagreed about others. I told him that, when in doubt, that if you address the needs of the plants, algae problems "magically" go away.
After reading BryceM's statement in another thread I started thinking about why algae problems "magically" disappear, and I believe I have arrived at a reasonable explanation that gets at the root of why all types of algae occur in our tanks (excuse the long post!).

The observation:
In past experience, I have seen decent plant growth in green water blooms and even in green dust algae (GDA) blooms. The plants still grew and didn't seem to have any deficiencies, but the algae was definitely all over the tank. Similarly plants still grow perfectly well with cladophora or black beard algae (BBA) growing in the tank in visible quantities. What is the connection?

The explanation:
I think if bloom criteria (trigger) are met, algae will bloom whether or not the plants are doing well. This makes sense with observing algae blooms in the wild. Blooms of certain species of algae appear at distinct times of the year in direct relation to nutrient concentrations, presence of predators, seasonal events (for example: an excess of one nutrient due to rains, or a lack of another due to no rains, etc...).

For example, if a particular species of algae is environmentally cued to bloom when nitrate levels are low for a few days, it will bloom. Since most plants can stockpile nutrients to last them a week at the very least, the plants still have nitrogen available to grow with, they are not deficient yet so the problem isn't that the plant is unhappy which causes the algae to bloom, it is rather the fact that the species of algae is genetically programmed to recognize a particular set of conditions in order to grow.

It is possible that the plant will quickly begin to suffer after an algae bloom gets started since they are already running off reserves and now have to devote more energy and scarce nutrients towards the task of scouring the water for trace concentrations of the lacking nutrient.

I think the statement that "algae = poor plant growth" is usually the case, but I don't think it is 100% accurate in every situation. I think this association tends to be true because people generally don't realize that there is a problem until an algae bloom has been triggered and the plants have depleted their reserves. Since it takes quite a long time for a weakened plant to fully recover and produce heavy new growth after it has been stressed it makes sense that algae, requiring far fewer nutrients to get by, would run rampant until the blooming criteria are fixed and the plants resume their normal roles.

Going along with this idea, I think that the recommended range of nutrient levels (5-20 ppm nitrate, 2 ppm phosphate, etc...) is a range in which few species of algae are programmed to bloom at. I think this may be because over eons of time algae evolution has found it more adventitious to fill a niche in the environment that requires disturbance rather than constancy. For example, if algae and plants grew all the time, provided there were enough nutrients to support growth (i.e. plentiful nutrients 5-20 ppm nitrate, etc...), then they would have to compete with each other constantly for available food which means less energy for reproduction. The plants, being capable of blocking sunlight due to their height advantage and emergent growth could simply shade out any algae that tried to grow constantly causing it to be less successful than a species that was dormant for most of the year except when particular conditions signaled a possible advantage (like a seasonal change for example). In nature it is well documented that species who initially occupy the same niche tend to evolve away from each other over time so that their requirements do not overlap and competition is minimized thereby increasing the reproductive success of both species.

When algae blooming conditions are met (i.e. unstable tank conditions favoring a particular species of algae) the algae blooms until the trigger condition is removed. Sometimes that might mean the algae has found it most effective to simply complete one life cycle and then return to dormancy (GDA), other times it may mean continual blooming conditions until the trigger is removed.

I think we must also recognize that many of the species of algae we deal with in our aquariums have been taken out of their environmental contexts. These algae species have hitched rides from every corner of the globe so particular blooming conditions (like low phosphate levels for green spot algae [GSA]) might be particularly adventitious in the alga's native habitat due to a specific predator, competitor, window of opportunity etc... and now it is not so easy to determine what benefit the algae is getting from blooming in response to the trigger. The relevance of the trigger to the alga's survival has become lost in our home aquarium, but the blooming conditions have not (yet?) changed.

What I would truly find interesting is to find out the original environmental situation of a species of algae that constantly grows in conditions within the recommended range (10-20 ppm nitrate, etc...). I would bet that if such an alga existed that it would occur in water absent of aquatic plants.

As a point of interest:
With a bit of research and the help of an algae specialist I managed to track down the original environment type for Cladophora. Claudophora is native to fast moving stream environments that do not harbor aquatic plants in the water column but rather only on the bank where the plants do not compete with algae for the niche. Given this algae's evolutionary niche with no competing aquatic plants it makes sense that it is programmed to constantly grow if there are nutrients in the water since it has not had to compete for nutrients or light with aquatic plants like other kinds of algae.

In marine environments:
To further my hypothesis I would like to bring attention to marine algae. As any reefer knows having the most minute concentration of nitrates or phosphates causes algae growth. In the presence of nutrients usually some kind of hair algae takes over and wrecks havoc on every surface of their tank. I believe that this algae, like the clado, has evolved to grow at a constant pace if there are nutrients present since it has not had to fight for nutrients and light with aquatic plants. In fact, there are very few aquatic plants in the world that are able to live in the ocean like algae, and corals grow far too slowly to out compete the algae for nutrients and light. Therefore a majority of the algae species living in the ocean should grow at constant rates when nutrients are present and this is exactly what we see in real life. For example: kelp, macro algae, micro algae, diatoms floating about in the water column etc... all grow at constant rates when there are nutrients present, they do not go dormant and then spring to life en mass like in freshwater tanks. Naturally there are blooms of algae in the sea, but this is simple because the existing algae that has been growing just fine has been given a bigger stock of nutrients from which to grow. The extra nutrients are simply able to support more algae that has already been growing at constant rates all along in lower quantities.

In summation:
The majority of algae in our tanks are opportunistic bloomers because if they grew all the time, plants would out-compete them for nutrients and light and they would go extinct. To survive they lie dormant in some form until conditions signal them to grow for a short period of time and then return to dormancy.

Thoughts:
I want to invite people to comment on this idea and hopefully we can get a discussion going about it. Perhaps at the end of it we will understand the delicate balance between a beautiful aquatic paradise and an algae nightmare instead of chalking up all our success to
if you address the needs of the plants, algae problems "magically" go away.
(Thanks BryceM! :D)
 

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Zapins, that's a wonderful observation and explanation. I don't have much to add in the way of good discussion, but reading through your explanations I realized a few things in my own tank.

Over the past 3 months, I've had nearly every algae you can imagine at one point or another, and I've changed nutrient dosing in every way/combination, and end up 'controlling' one algae while getting a bloom of another.

I have a hunch now, that if I just stick to a good routine, the algae will go through it's cycle and return to dormancy. My main problem is a lack of patience, I believe. I've been making too many adjustments too quickly.

Any thoughts on that?

-Dave
 

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Discussion Starter #3
I agree, try keep the nutrients consistent, and try dose nutrients within the "golden plant range" (5-20 ppm NO3, 2 ppm PO4 etc...) for 2 weeks or so until the algae bloom finishes. Things should settle down soon!
 

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Nice stuff Zapins.

I think my own understanding of this is to the point that I can make a few fairly solid comments:

1. I agree that stressed plants take a long time to recover once favorable conditions return. Depending on the species and setup, this can take 2-6 weeks.

2. The notion that a measurable level of macronutrients in a planted tank will lead to algae issues is not a correct one. (This was actually the basis of a recent article in TFH).

3. The growth phase of algae is multi-factorial, and simple availability of what algae need is not sufficient to lead to nuisance levels of algae.

4. Not all aquariums are created equal. What works in one situation will not always be appropriate in another. There are exceptions. Green water always dies with UV, etc.

5. There is an relationship between light intensity and the precision required of a person to keep conditions steady.

6. Algae are smarter than us. They are also more patient.

7. No matter what, you will encounter algae issues from time to time. It is like a chronic medical condition that can never be cured, but does respond to careful management.

8. When in doubt, work to meet the needs of the plants.

9. When things go bad, look to yourself first. Don't skip dosing, be careful with your math when mixing solutions, keep filters cleaned, etc. Slacking off on my fertilization and maintenance program has been the real issue with many of my own algae battles.
 

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Good discussion here, and real nice write up Zappins! I will echo what others have said in that consistency and patience are of utmost importance.

I recently switched water sources on my 10 gal going from my well water liquid rock (kh11), to my son's city water with kh 3-4 as an experiment to see if I could grow some of the plants I'd always failed miserably with (R. macranda). Before the switch, the tank was what I called algae free, which meant gsa on the glass, but otherwise clean. After the switch, which occurred about 6 weeks ago, the gsa has pretty much disappeared, but I have what looks like a staghorn/hair algae cross sprouting all over the tank. I'm hoping time, consistency and the Amanos I'm about to put in there, will return things to a clean state. But even with the algae outbreak, the plants continue growing at a normal rate.
 

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good no-nonsense list Bryce.

If I notice any magic to a tank with an algae free appearance, its that the algae cant tolerate disruption
as much as plants. If I neglect a corner of a tank, or don't keep sediment off the leaves, etc. any
lack of good husbandry - the algae will take advantage of this and then I have work to do cleaning it up.

If I pester the algae, pull it off leaves, alter flow, swish around sediments and then change water for example;
It stops blooming and suffers, where nutrient levels stay the same and the plants are still doing well.

Nice stuff Zapins.

I think my own understanding of this is to the point that I can make a few fairly solid comments:

1. I agree that stressed plants take a long time to recover once favorable conditions return. Depending on the species and setup, this can take 2-6 weeks.

2. The notion that a measurable level of macronutrients in a planted tank will lead to algae issues is not a correct one. (This was actually the basis of a recent article in TFH).

3. The growth phase of algae is multi-factorial, and simple availability of what algae need is not sufficient to lead to nuisance levels of algae.

4. Not all aquariums are created equal. What works in one situation will not always be appropriate in another. There are exceptions. Green water always dies with UV, etc.

5. There is an relationship between light intensity and the precision required of a person to keep conditions steady.

6. Algae are smarter than us. They are also more patient.

7. No matter what, you will encounter algae issues from time to time. It is like a chronic medical condition that can never be cured, but does respond to careful management.

8. When in doubt, work to meet the needs of the plants.

9. When things go bad, look to yourself first. Don't skip dosing, be careful with your math when mixing solutions, keep filters cleaned, etc. Slacking off on my fertilization and maintenance program has been the real issue with many of my own algae battles.
 

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Discussion Starter #8 (Edited)
Thanks everyone for the comments so far on my idea.

I am specifically interested in starting a discussing of the idea's shortcomings rather than discussing some of the old generalizations up until this point. At the end of the discussion (if there is an end) I want to piece together a better theoretical understanding of what makes algae grow in our tanks rather than a nonspecific list of generalizations. Potentially something that could be tested for or surveyed.

In particular:
1) Did you read the entire article?
2) Are there any glaringly obvious flaws with the idea I proposed - if so, please outline them clearly and give evidence of some kind.
3) Are my examples sound? Did I generalize too much or not enough?
4) What do you think of the idea itself? Does it seem to make sense?
5) If I, or someone else were to make an actual experiment to test part of the idea what would it be? Surveys of wild habitat? Algae + fertilizer tests? Specify as much as possible.
6) If anyone knows the origins of any specific type of algae, or where it does best in the wild (I.e. with aquatic plants, or in lakes with no plants, lakes with ponds, streams, etc...)
7) To a lesser extend, I would like to know if there are any personal experiences you have had that either match the concepts put forth here or go against them. Explain as much as possible.
8) Anything else that is relevant to understanding algae better.
 

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Hi Zapins,

It seems to me that if you were to test, you would need to do so in an aquarium, not in the wild -- as that is what we are interested in on the forum. :D

The testing would have to hold all points constant except the one being tested; i.e., the trigger you are trying to create. So the pH, kH, etc. should be noted and should be the same across the board as you try to recreate the triggers.

Just my 2 cents.
 

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Zapins, excellent stuff here. I actually explained the EI method to a couple of professors here at UF. One suggested allelopathy might be the reason, the other suggested that the algae may only bloom when it 'senses' low nutrients. He suggested the algae evolved to rapidly multiply and reproduce when it senses bad conditions to ensure survival (Spores maybe he didn't know what type of algae i was talking about).

In particular:
1) Are there any glaringly obvious flaws with the idea I proposed - if so, please outline them clearly and give evidence of some kind.
Well i don't think the focus should solely be on lack of nutrients that causes the bloom. Maybe type of nutrient. NH4 is much preferred by algae so maybe as soon as a 'dormant' cell get a sip of NH4 is reproduces. Best evidence i have is that when i leave old leaves to rot in my tank i immediately get algae growth (OM breaking down, not enough for a 'bloom' but noticable increase). After all its not a very good idea to rely on blooming when there is not much material to bloom with (I know they don't need much but its just a thought).

2) Are my examples sound? Did I generalize too much or not enough?
- I'll admit i didn't read the whole thing, i am taking a break in the library. I thought it was an excellent evaulation though.

3) What do you think of the idea itself? Does it seem to make sense?
Yes it makes sense BUT, obviously this subject is going to be more complicated because each algae is a totally different organism. Their evolution might not coincide. Nobody is going to pay a scientist enough for him to figure this out so assumptions are our best bet i think.

4) If I, or someone else were to make an actual experiment to test part of the idea what would it be? Surveys of wild habitat? Algae + fertilizer tests? Specify as much as possible.
I don't think natural bodies of water are applicable. To bring a lake up to 20ppm nitrate would be absurd... the amount of nitrate would be enormous. What we have to realize is plants grow on the banks and shallows of lakes. The majority of most lakes do not have plants or algae in the center (Majority of volume). .00001 PPM nitrate is still a massive amount, the plant mass needed to utilize that is most likely not in the lake. Concentration gradients are going to bring the ions to the plant so the plant will never run out of nutrients even if the lake has low concentrations. This needs to be done with aquariums. I might have time to work out an experiment later but honestly thats a lot of writing and its kind of complicated. I would probably need help from a PhD.

6) To a lesser extend, I would like to know if there are any personal experiences you have had that either match the concepts put forth here or go against them. Explain as much as possible.
I have observed a drastic reduction in pearling when nitrite is present in a tank (no other changes). the plants are not photosynthesizing and this could cause algae problems. Cause of nitrite spike could have been over feeding in a newly cycled tank. I had some births and was over feeding to try to keep the parents from eating the babies. THis has occured 3 times now, when i see plants reduce pearling i test for nitrite and everytime its there. 4 days later nitrite 0 plants blinged out.

Great stuff man.
 

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I'm not pooh poohing after all we are all here to have beautiful tanks and therefore discussion on these subjects is something to be welcomed, however......

I pretty much agree with Bryce (apart from the 2ppm of PO4 as I dose 5ppm ;))

I have no algae in my tank yet I dose full EI under what you guys would call low light (pre LEDs that I put in a few weeks ago I had T5HO - 0.9WPG for the 9 hour period with a noon burst of an extra 0.5WPG.)

I do not vacuum the substrate. I empty the water from the filter hoses.

I do not clean leaves.

I do not clean up used food, I leave it!!!

I used to have various algae problems. Then I changed 1 thing and haven't seen algae since!!!

I added a Koralia1 which bumped my flow from 5.6x to 17.6x turnover per hour!!!

So my conclusion (which may be wrong ;)) is that flow was the cure. Not just cleaning plants and keeping detritus in suspension but also circulating nutrients better and more importantly improving CO2 circulation!!!

I have some fern leaves that are disintegrating after being damaged yet there is no algae present. There are a couple of damaged leaves that look like madagascar lace plants but still no algae on the 'wound'. I haven't trimmed them because I want to see how far they will disintegrate without triggering algae but so far it looks like they may just fall apart with no algae!!!

AC
 

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Maybe that is a function of the low light? Could you tell me the time from of start-up to algae to adding the koralia and fix of algae problems?
 

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Zapins,

My only hesitation here is that we shouldn't over-simplify the question. We're naive if we think that the different forms of algae respond to identical mechanisms. In some planted-tank circles, people even exchange algae to try to inoculate their aquariums with algae that is less prone to be a nuisance.

The more I play around with aquariums, the more fascinated I am at the complex interactions that take place with these unbelievably simple, yet complex, single-cell organisms.

I'm nursing a couple of "pet" theories. Maybe they could be incorporated into any experiments that you can design. One is that healthy plants have an ability to "fight off" algae "infections". Plants don't have a classic immune system in the same sense as vertebrate animals, but they do possess some pretty solid innate immunity systems. These systems would probably apply more to BBA type algae, which often invade the actual plant tissue. Old, sick leaves are the first to be affected IME.

Diatoms and thread, OTOH, tend to just coat the surfaces of the plants.

Complex stuff.......
 

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I won't go on about the light. What I am implying is I am dosing Full EI (supposedly for medium to highlight tanks and CO2) so there is more than excess if it is indeed low light.

The scape was set up in July 2008. It was algae free at the beginning and was lean dosed. The flow at this time was 5.6x using just the filter so in reality allowing for flow restrictions 50% x 700lph = 350lph / 125Ltr = 2.8x

The algae started when the plantmass got larger and larger (the sig pic is the scape in question) and there were all the usual suspects there (rhizo, clado, BBA, GSA, GDA.)

As the plantmass grew the flow reduced as plants become barriers to the flow. This meant CO2 was not so good either and I was getting a dark green DC when it had been almost yellow from the beginning. I ended up at 5bps to get to mid green whereas it was on 2bps before the algae war

I tried several combinations including using a tradition 400lph powerhead trying to sort the problem but eventually gave in and bought a Koralia 1 (150lph with minimal flow restrictions) in Mid December.

This managed to get the CO2 into the yellow on both DCs with the improved circulation. I ended up back at 2bps and getting a nice lime green almost yellow :)

Algae was virtually gone within a couple of weeks.

S since having the Koralia in there for nearly 2 months now I have no algae apart from a few leftover blobs of GSA on Anubias leaves. If plants do get damaged and deteriorate I no longer get algae on the damage which I had always believed was inevitable (ammonia leeching = algae at source.) This has proved that it isn't the case unless I have a magic fern :lol:

I haven't cleaned the glass for many a moon. I don't get GDA/GSA on theglass. I let it go through a 4 week cycle at the beginning and it never returned!!!

AC
 

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Let’s get back to general algae talk and not what’s happening in one person’s tank. I agree that “addressing the needs of the plants” is just one part of the equation.

There are very few guaranteed solutions IMO to algae issues in each person’s tank since every tank has so many different variables it would be difficult if not possible to analysis the effect each one has on each other and the alga that results. Many times in the threads there are scientific solutions offered to one’s algae issues which end up solving nothing or possibly making the algae worse. Trying to pinpoint someone’s algae issues is sometimes like playing pin the tail on the donkey.

That being said, I do believe there is a direct and dare I say indisputable relationship between organic control, light and algae.

I like to use the example of a swimming pool since it seems to be straightforward.
A pool sits outside in massive amounts of light. We dump chlorine in the pool to kill any organic matter. Without chlorine the pool would quickly fill with algae. The more sunlight the pool receives the quicker and more profound the algae is. This combination of water, light and organics exists in our tanks as well. Unfortunately our tanks are more complex and we can’t simply dump chlorine in to control algae, but without a doubt there are parallels.

In the tank the bio-filter, organic filtering products and the ability to adjust light duration takes the place of the chlorine. Organic control is a very broad term. Healthy plants, bio-media, carbon, products like Purigen all are subsets of organic control. As well as limiting food, fauna and the removal of dead leaves from plants since they all either remove or add to the organic levels in one’s tank.

Most algae issues take place soon after startup. At startup the ability to control organics is challenging since you don’t have a mature bio-filter in terms of plants and media. To fill this void carbon, purigen, seeded media and water changes are used in tandem with a reduced light duration. I have started up many tanks this way and have never had a nuisance algae issue if these steps are followed:

Seeded bio-media
Carbon/Purgien
Light duration ~ 6hrs.
No livestock 1st month
Remove any decaying plant matter
Weekly 50% water changes
Large Plant mass fertilized as needed

If the tank is high light and/or limited plant mass (iwagumi) it is even more important to follow each and every one these religiously to avoid issues. Once the plant mass starts to grow and the bio-colony expands some of these can be relaxed like the removal of carbon and increasing the light duration. IMO healthy growing plants help control algae, but they are only a part of the organic control process. I don’t pretend to know the levels and/or reasons why an algae bloom might get triggered. I think this would be almost impossible going back to my opening paragraph. But I do know when I apply the steps above to my tanks, I do not get algae. Predicting what triggers an algae bloom, IMO is like predicting the stock market. There are just too many variables to consider. This is where experience comes in.
 

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let me throw in 2 other variables -- O2 and CO2 levels. More as a hypothesis and not a firm conclusion.

When tank plants are pearling, O2 is saturated. Algae is often not present. Does the algae find it harder to develop because the plants are healthy and are sucking/storing nutrients making them unavailable to algae in the water column (assisted by good water flow)... and there aren't any dead leaves to leak nutrients... or does the high O2 by itself somehow inhibit algae (say, analagous to H2O2 treatment)? The algae limited nutrients under good plant growth could be one of the traces, particularly if N, P, and K are maintained at high levels. Such nutrients may only need to be limited for short periods, not all the time.
Also, does 30+ppm CO2 in some closed planted aquaria situations also inhibit algae, again when there is sufficient flow to keep it well mixed in the water column. In fact, the combination of CO2 and O2 may also be a factor, something that is not typically found in nature; particularly in fast moving streams where O2 but not CO2 can be high.
These are purely speculations and not something i have seen in the literature....throwing it out for reaction.
--Neil
 

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I think that so far we have three good idea's going

1. Lack of nutrients cause algae to bloom as a responce to try to expand to higher nutrient areas. or to survive the low nutrient levels by sheer numbers.

2. NH4 released by organics breaking down causes algae blooms. THink of it this way. The nitrifying bacteria are on surfaces... so rotting organic matter releases and NH4 either the NH4 makes it close to a surface and is affected by bacteria, or an algae strand hits it. the organics slow release this nh4 so there may be just enough NH4 that the algae reproduces very slowly and is manageable most of the time. However when something disrupts the bacteria just a little bit the algae gets enough of a cencentration of NH4 to bloom. Algae can also use NO3, but not as readily i dont want to confuse anything.
---About the tank with low light, rotting organics and low algae. I believe there needs to be a certain threshold of light also for the algae to bloom. Sunlight is much brighter than the brightest t5 HO or VHO set-up.

3. Allelopathy which i can't personally make much sense out of. unless the chemicals have a very shor half-life, they would build up in the water.
 

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One could add the perfect algae removing device to their tank, and unless the tank is located within a purfied and sterilized vacuum, algae will always be in the water. As they are on the microscopic level, they are able to ride air currents; in fact, you are inhaling them as you read this. I think that this needs to be understood for the "novice" who may be reading this. You will NEVER get rid of algae in your tank, and I believe that this article really concentrates on prevention. Even those who are fortunate enough to not have GSA on their glass or mounds of clado growing they can always get it if a parameter of prevention is not followed or one gets too comfortable and follow the routines associated with prevention. It is very difficult to get rid of all organic decay in a tank, but if all other parameters of prevention are followed, one shouldn't need to rid their tank of ALL decay rather just most of it. It is when a combination of key guidelines are not followed do the environmental conditions become favorable for an algal bloom or growth. The aquarium water could be completely sterile of algae and hypothetically speaking, so could all of the plants, wood, substrate, etc., but algae will always be present in the tank.
 

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So my conclusion (which may be wrong ;)) is that flow was the cure. Not just cleaning plants and keeping detritus in suspension but also circulating nutrients better and more importantly improving CO2 circulation!!!
AC
I am not an expert and would love to find the best technique to keep algae minimized at all times. However, I would agree with the observation that flow is an important parameter.

I have an XP3 on my 50g and recently noticed that the flow was getting severely reduced due to fouling but I didn't have time to clean the filter. At the same time I also noticed a large increase in algae and little to no pearling even though my CO2 drop checker said there was plenty of CO2 around. I finally got around to cleaning the filter out and there is now so much pearling that even the tank walls are coated with bubbles. Improved flow was the only change. So I'd say that good water flow is a variable to keep in mind with any designed experiment.

Those out there who are familiar with mass transfer film theory will say that with poor bulk water flow the film thickness on leaf surfaces increases reducing the rate at which nutrients can be absorbed by the plant, even if they are readily available in the water column. Just because a nutrient is in the water doesn't mean a plant can use it. It has to get to the plant's cell membrane before it can ever be absorbed.

So maybe it's not just a lack or excess of a nutrient(s) that could cause an algae problem, but also a lack of availability to the plants that can cause a problem. This would include cases where poor water flow past the plant surface leads to a localized lack of availability. If the flow gets too bad large portions of the plant population could be having difficulty getting to the nutrients causing them to suffer and allowing excess to exist in the water column for algae to take advantage of.

I don't think good flow is a magic cure all, there have been several good ideas presented so far in this thread, but I think good water flow is probably important enough to be kept on the list of variables to check, or at least monitor. As one experiment, it would be interesting to run two tanks with the same set-up and nutrient concentrations in the bulk water and have one with vigorous flow and one with very limited flow to see where and how much algae grows in each.

Of course now that I think about it, which was the bigger impact to algae production, significantly increasing the bulk water flow throughout the tank or removing a lot of detritus from the filter media? I think the improved flow was likely the cause of improved pearling, but was that also the direct or indirect cause of a reduction in algae growth??? :confused:
 
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