# Does too much phosphate cause algae to grow



## Vaevictus

Hi all,

I keep reading conflicting information on the net on the effects of phosphate on algae growth.

On this forum I more often than not see comments suggesting that a lack of phosphate causes algae to thrive, and adding it will stop algae growing.

Other sites suggest too much phosphate causes the algae, with people going to great lengths to keep phosphate levels 0.

Which is it?

Vae


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## captain_bu

Vaevictus said:


> Other sites suggest too much phosphate causes the algae, with people going to great lengths to keep phosphate levels 0.
> 
> Which is it?
> 
> Vae


This is old-school thinking. Phosphates are necessary for good plant growth. If it was definitive that phosphates themselves caused algae than everyone who dosed phosphates would have tanks full of algae and that is simply not the case. 

Limiting phosphates can seem helpful in preventing algae since phosphates help drive CO2 uptake, if you are getting algae because your CO2 levels are not what they should be and you limit phosphate the tank may do a little better due to the lessened demand for CO2 but you do need phosphates to grow plants. Zero phosphates is not a good thing for a planted tank. Shoot for at least 1ppm if you want to keep them in the low range but don't stress if they go higher. Lots of people successfully eradicate GDA or GSA by intentionally raising phosphate levels.


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## Wasserpest

If Phosphates are the limiting factor for plant growth, adding them will definitely help to combat algae, as with better plant growth, algae will be suppressed.

If, on the other hand, something else is amiss, adding Phosphates will surely feed any algae that are already growing there, so some might have come to the conclusion that P will cause algae growth. Not quite right...


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## plantbrain

Wasserpest said:


> If, on the other hand, something else is amiss, adding Phosphates will surely feed any algae that are already growing there, so some might have come to the conclusion that P will cause algae growth. Not quite right...



So **if** something else is really amiss..........then is not that something else ......... is the cause/issue/alternative and not PO4?

Why would adding PO4 cause an issue more so than without if it's something else?

Since we are adding high PO4.........what difference would it make to algae?
They are not limited in either case. Folks say this often, I'm just asking is there any basis to it.

If so, where's the logic and test to demonstrate it? I've never been able to show it in any quantifiable manner. Would it not depend on the intensity of something else(say CO2 or too much light), not whether the PO4 is high or low?

Is increased PO4 not simply an artifact of of poorer plant growth/care? 
If I limit CO2 suddenly, I'd expect my N and P to rise if all else was kept equal, since less CO2= less N/P uptake........

I'd suggest that co limitation is extremely rare in aquariums.
Some bobbing between PO4(if they limit it) and CO2 is likely much more common.

When they add PO4 under a lower CO2 ppm, they increase plant growth and the CO2 drops below a critical value. When they limit the PO4, then the CO2 is okay and no algae. Since plants can handle some fairly strong PO4 limitation, this can occur with decent results still. But does not imply that under other conditions, adding more PO4 will encourage algae any more than a limited amount.

The algae are not limited in either case, only the plants.

Regards, 
Tom Barr


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## tuvix72

Key word is "balance" between all the nutrients. An imbalance, be it in PO4 or other element, is more often the cause of such problems. I've had nice results with tanks ranging from 0ppm to 3ppm of PO4, obviously very different tanks, but the key was getting that balance dialed in among all the elements, including CO2.

I agree it's "old-school" mentality to constantly hammer phosphates and/or nitrates as the key cause of algae. Today I tend to hear this more from reefers getting their thumbs wet with plants for the first time... it brings chills for them to think we want to dose PO4 and NO3! :icon_eek:

Cheers,
Giancarlo Podio


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## Hoppy

I think that "balance" is much less important than some others think. As long as you have good CO2, consistent with the amount of light you have, and have non limiting amounts of all the other nutrients, it doesn't matter if you have 2 or 3 times the recommended amount of any one of the nutrients, as far as algae problems are concerned. Most important, in my opinion, is making sure only the light is restricting how fast the plants can grow. That way the plants will be healthy and growing well, consistent with the amount of light you have. And healthy, growing plants are what discourages algae from even starting.


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## farmhand

Hoppy said:


> As long as you have good CO2, consistent with the amount of light you have, and have non limiting amounts of all the other nutrients, it doesn't matter if you have 2 or 3 times the recommended amount of any one of the nutrients, as far as algae problems are concerned.


My guess as to why people have a problem with this concept is that they are thinking like a doctor prescribing drugs. They are afraid of an OD in their tank. :eek5: The same rules do not apply here.


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## MarkMc

Hoppy, you are IMO 100% right. Most of us that have had planted tanks for a long time have been through the "I need phosphate or nitrate remover to fix my algae problem" or "it must be my lights-I should bite the bullet and get those metal halides" or whatever. I'm finding out that the fertilizer level is not important as long as you have what the plants need when they need it AND that is all driven by the light/CO2 equation. I may be wrong but I'd say that too much of any part of NKP will not be a problem as long as you have light/CO2 mastered. Big weekly water changes are important too. The whole philosophy of EI is to simplify things if I may say so. Test kits? Who needs them! pH? Fuhgetabowdit! gH and kH? If you have running water-use it! I do not miss hauling my RO water from the basement that's for sure.


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## gpodio

Hoppy said:


> I think that "balance" is much less important than some others think. As long as you have good CO2, consistent with the amount of light you have, and have non limiting amounts of all the other nutrients, it doesn't matter if you have 2 or 3 times the recommended amount of any one of the nutrients, as far as algae problems are concerned. Most important, in my opinion, is making sure only the light is restricting how fast the plants can grow. That way the plants will be healthy and growing well, consistent with the amount of light you have. And healthy, growing plants are what discourages algae from even starting.


Agreed, nothing should be limited in a planted tank and healthy plants are indeed the solution to keeping an algae-free tank! Allelopathy?

But I'm not sure I agree with not having a target range, balance or cap on nutrient levels, specially some of them. Some elements at certain levels can inhibit the uptake and/or use of other elements by the plants, for example potassium can effect calcium absorption. Some elements can also become toxic beyond certain concentrations, usually trace elements. On the opposite end, the concentration of an element can effect it's uptake rate due to osmotic pressure differences... While I don't give a huge importance to fixed ratios, like the redfield ratio for example, I do feel that several elements have an ideal range which we should try to keep them in, hence my use of the word "balance".

With PO4 for example, I have played a lot with over the years and in particular when it first started to emerge as a not-so-nasty element back in the day. I have indeed triggered green water in an otherwise very healthy planted aquarium by raising PO4 levels beyond 5ppm... If there's a way to keep such a level and still be problem-free, I would imagine it involves raising or adjusting the other elements including CO2, light and perhaps even plant mass or speed of growth, reinforcing the concept of a sort of balance if you look at the entire system this way.

Regards,
Giancarlo Podio


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## gpodio

MarkMc said:


> Hoppy, you are IMO 100% right. Most of us that have had planted tanks for a long time have been through the "I need phosphate or nitrate remover to fix my algae problem" or "it must be my lights-I should bite the bullet and get those metal halides" or whatever. I'm finding out that the fertilizer level is not important as long as you have what the plants need when they need it AND that is all driven by the light/CO2 equation. I may be wrong but I'd say that too much of any part of NKP will not be a problem as long as you have light/CO2 mastered. Big weekly water changes are important too. The whole philosophy of EI is to simplify things if I may say so. Test kits? Who needs them! pH? Fuhgetabowdit! gH and kH? If you have running water-use it! I do not miss hauling my RO water from the basement that's for sure.


But the EI does itself indicate ranges for each element, does it not? And if light and CO2 levels play into the viability of keeping very high macro levels... isn't that a balance of sorts? EI helped us come out of the limiting mentality, reinforced the importance of CO2 levels and simplified the entire management of nutrients by basing itself on what is dosed and not what is left in the tank... but I don't think we can just dump any amount of nutrients in the tank.

I've been out of these forums for a couple years... perhaps I'm just becoming outdated with the new concepts in our hobby... But I strongly feel one cannot just add as much macros as they like and as long as CO2 and light are well maintained it's all going to be good... is my mentality in regards that outdated already?

Regards,
Giancarlo Podio


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## hbosman

Algae is very small so, they can't really be nutrient limited. Put a glass of water in the window sill. Don't put any chemicals, nutrients or animals in that water. The water will develop algae correct? I think that indicates that algae don't need you to add anything. This being the case, you might as well add plenty of nutrients for the plants perhaps, adding a little extra to allow wiggle room (Estimative Index). The only chance you have against algae is lots of CO2 and lots of healthy plants. Light level is the only way to limit algae. You don't want to add "extra" light, just enough to grow your plants well. Some people hang their lights so they can adjust the light level by adjusting the light height. Others use timers to adjust light duration and may even use multiple timers to limit how long all of the lights are on for. The multiple timers allow you to blast all of the lights for just long enough to get the desired growth while giving you the option to cut back some of the lighting when algae gets out of control. Adjusting light height, duration and intensity is still much easier than using calibrated test kits, scales, RO water etc....


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## plantbrain

gpodio said:


> Agreed, nothing should be limited in a planted tank and healthy plants are indeed the solution to keeping an algae-free tank! Allelopathy?


Between simple experimentation by myself and some other failings, Ole pointed these out, I took a very different critique on the matter, this does not bode well in any likelihood.



> But I'm not sure I agree with not having a target range, balance or cap on nutrient levels, specially some of them. Some elements at certain levels can inhibit the uptake and/or use of other elements by the plants, for example potassium can effect calcium absorption.


So how much ppm and difference is required for this in exogenous conditions like in aquariums, Hydrponics or???? Nice to speculate, but I've seen no evidence at all for this in aquariums.

Just because Ghori claimed to see it in a tank or two, does not imply it's what was causing the issue he had. I and others added high K+ and had low Ca++(Like most folks in the SF bay area do anyway) and found not correlation, thus this hypothesis has been falsified. This is a sure thuing, why Ghori or others saw correlation in their tanks remains unanswered however, thus they cannot conclude, whereas I can in saying high K+ does not inhibit Ca++ uptake.

At least up to 50-100ppm K+ and low Ca++ 4ppm or less.
Hydroponic solutions typically use 200ppm + or more K+ and these can rise to 300ppm, and we still see no stunted or Ca++ inhibition. We also cannot say as aquarist without doing Ca++ tissue analysis of the treatment if in fact it's Ca++. Correlation is simply never enough when there's counter test that show no such issues.

Folks mistake Ca/K signalling pathways that are endogenous cell mediated micro/millmolar concentrations and growth/uptake. Tyhese are two very different things that have been confused.

I really do not know what ppm's is required for inhibitory effects for most of the nutrients, I suspect most are in the salt stress ranges, which are hundreds of ppm's, well above Hoagland's solution levels, which are 52ppm for P, 235 ppm for N, 210 for K+ etc........... 

I think we are an order of magnitude less, even if we muck up by say 5x, we still are okay, even with discus and shrimp, Tonia or any wimpy plant of choice.

While many put forth hypothesis...........all it takes is one test to prove the hypothesis incorrect, while all the testing in the world may never prove the hypothesis correct. This is how falsification is. :icon_idea



> Some elements can also become toxic beyond certain concentrations, usually trace elements.


I think for copper, this can be stated, I do not know for the others.....
0.4ppm for algae, most inverts
1.0 ppm or so for plants..........



> On the opposite end, the concentration of an element can effect it's uptake rate due to osmotic pressure differences...


I do not think this plays a large role for limited ranges, cells are pretty good at massive differences between internal and external differences, some of them 10-15 orders of magnitude. It can be hard for plants to exclude salts however........I think this is where this above situation, becomes problematic. At the excess salt stress level.




> While I don't give a huge importance to fixed ratios, like the redfield ratio for example, I do feel that several elements have an ideal range which we should try to keep them in, hence my use of the word "balance".
> 
> With PO4 for example, I have played a lot with over the years and in particular when it first started to emerge as a not-so-nasty element back in the day. I have indeed triggered green water in an otherwise very healthy planted aquarium by raising PO4 levels beyond 5ppm...


As I stated earlier, all it takes is one example to disprove the stated hypothesis, I add 5ppm 3 x a week to this tank, well in excess of 5ppm total residual and I have never induced any such algae, let alone GW:










And another tank:









And another:










So it's not just one special tank........it's a generalized response, or lack of one in this case.

CO2/light etc, are larger players.........and far more likely to explain differences in such results. Adding to that, light and CO2 are the most poorly measured of any parameters. So folks tend to be bias towards ppms and nutrients in their assumptions.

This is unfortunate and hopefully this will change.



> If there's a way to keep such a level and still be problem-free, I would imagine it involves raising or adjusting the other elements including CO2, light and perhaps even plant mass or speed of growth, reinforcing the concept of a sort of balance if you look at the entire system this way.
> 
> Regards,
> Giancarlo Podio


Oh you _wise sage_ you:hihi:
You got it and know where to look.

The entire system, that is the key, not so much looking at ppm's and micro management.

Light drives => CO2 which in turn drives nutrients, sort of obvious and simple concept, but it is used to better manage a given horticultural goal. With less light, I get higher CO2 use and light use efficiency. It is easier for me to add CO2 and places less stress on fish since there's less demand and the total ppm target is less for CO2.

This in turn means less demand for nutrients, so my range for non limiting ppm is much larger, as if I do limit something, the resulting intensity is also correspondingly less. So there's just a mild effect, not disaster:icon_idea
If you limit light and then limit CO2, now you have an extremely robust method: non CO2. Many non CO2 planted tanks have high PO4(several ppm) and low N and they persist for months without change.

I think aquarist are better off looking at these other factors and how they tie together to explain things more and to look at better ways to manage algae, rates of plant growth, various problems they encounter.

We spent a lot of time playing with nutrients, suggesting ranges, adding just enough etc, but gave much less consideration to light. Why not limit things with light? Why not add just enough light??? Why not squeeze every bit of growth out the plants with the lower light? Are we not wasting light/energy/electric bills using more than we need for nice growth/good rates of growth??

Algae are not limited by CO2/nutrients, but what about light?
That's the only parameter I can think of where they might be.

I've long heard that adding non limiting nutrients is "wasteful", but why is this not applied to light? Electric cost a lot more than any nutrient excess and adding more light stresses CO2 management/addition, nutrients, etc.

This gets to very fundamental issue with algae, management and rates that we want/have as goals. Nutrients? Not very much, it's more the tail wagging the dog there.

Good to hear from you!!!

Tom Barr


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## plantbrain

gpodio said:


> But the EI does itself indicate ranges for each element, does it not? And if light and CO2 levels play into the viability of keeping very high macro levels... isn't that a balance of sorts? EI helped us come out of the limiting mentality, reinforced the importance of CO2 levels and simplified the entire management of nutrients by basing itself on what is dosed and not what is left in the tank... but I don't think we can just dump any amount of nutrients in the tank.
> 
> I've been out of these forums for a couple years... perhaps I'm just becoming outdated with the new concepts in our hobby... But I strongly feel one cannot just add as much macros as they like and as long as CO2 and light are well maintained it's all going to be good... is my mentality in regards that outdated already?
> 
> Regards,
> Giancarlo Podio


I agree 100%.
There's no need to add a lot more than we really need out side some reasonable amount based on demand/uptake.

We have a large room for error already.










In the above figure, we can use uptake by plants, or nutrient concentration in the dry matter, these are conceptually equivalent along the x axis.

D has the largest range, but there's no need to go that much beyond the C range, you can and without problem over a large range, but why? 
If there is no real benefit........there's simply no need and you end up just wasting the ferts, even if they are essentially free/cheap etc.......*all we need to do is provide a large enough range that we do not risk getting limitations.*

More is pointless unless you are simply curious as to what might happen.
But not as an on going method. I add a lot more than the C range for PO4, but it does seem to help the plants, we all tend to add a lot more K+ than we need to target the C range. If you have lower light/good CO2, then the A and B range are not nearly as steep, they are more gradual, with higher light, then become steeper and thus harder to keep within and good range for management.

It can be done with more light, but there is less room for error, slopes will be steeper.

Many folks end up in the B range, which can reduce the uptake of CO2, thus when they add more PO4 (or what ever nutrient of choice here), they often get algae. This indirect since now the CO2 has become limiting. Liebig's law applies to cO2 and to light for that matter in our aquarium planted tank case.

I think this is the best article on CO2/light even though I do know the authors personally:

http://www.tropica.com/article.asp?type=aquaristic&id=142

Regards, 
Tom Barr


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## mistergreen

Interesting. So as long as you supply ample light, CO2 and a little nutrients. You're fine.
So there shouldn't be any distinction on which fert system is better like EI, pps pro, or PMDD; as long as the plants aren't showing any signs of deficiencies.


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## plantbrain

mistergreen said:


> Interesting. So as long as you supply ample light, CO2 and a little nutrients. You're fine.
> So there shouldn't be any distinction on which fert system is better like EI, pps pro, or PMDD; as long as the plants aren't showing any signs of deficiencies.


ADA etc as well, or sediment based ferts can be added in this scenario.
But with lower light, most any routine that's done will work, even plain old fish only waste.........which was the old school thought process.

Since less light = less demand, so less dosing tend to work fine there, but not as well as you increase light. Since we rarely compare light on equal terms and CO2........this has led to some claiming nutrients are everything and all important, when in fact, the reversed is more true.

As long as the nutrients are in the C/D range, you will have 90% or more critical concentration/optimal growth rates. Since each method adds the same things, and they target the same range on the graph, are they really that different?

No.

That is why I chose high MH light to see how high I could go on the D range to cover any higher light tank, without having to account for all the variation different aquariums might have. From there, anyone can reduce it down till they see a negative response and then bump the dosing back up to the next highest level easily(or just leave it). If it's non limiting there, then it's non limiting for any aquarium. This got around the light comparison issue.

If you target B range, then you run a much large risk of limiting nutrients and having confounding effects on CO2/light use because of that as well as reduced growth rates. If you want reduced growth rates, well.......then use less light, stop wasting it/making things harder on yourself.

PMDD was developed with about 20-40micromols of light, very low light indeed. It also has PO4 in the B range, sometimes A range, which influences CO2 demand(reduces it). When folks add PO4 to non limiting levels, then the CO2 demand also goes up as well, if it's not adjusted to compensate, then you end up with algae, not due to PO4, rather, not making sure CO2 was independent.

We can go back and test with CO2 higher and realize that there's no algae and nice better plant growth/health as a test and falsify the hypothesis. Paul and Kevin did not do this with PMDD, I and Steve Dixon stumbled upon it and started scratching our heads.

EI is 90% PMDD, just dry weight 2-3x a week vs solutions daily/richer CO2/less chemistry/a bit more water change. PPS is virtually identical to PMDD however and gives no credit to the method which is almost a carbon copy of. It's not like folks did not long know of PMDD prior to PPS.

Why co opt something, call it your own and not give credit?
Targets for Fe, CO2, PO4, NO3 all are virtually identical.

EI does not come close but gives plenty of reference and got a lot of back ground from PMDD. Heck, doing water changes, adding ferts back, we all do this at some level. Dry vs liquid makes no difference. Daily vs 2-3x a week makes no difference either. 

All that does matter is adding enough for a given light/CO2 rate to match plant demand. 

Why bother with dosing or worrying about every last ppm when you can add ADA AS or mineralized soil/worm castings, Osmocoat etc and then have even more fudge factor? And with lower light, you have even more.
Now you can do fewer water changes with less issue if that's your goal.

Growth is still very good and very easy to manage.
Want more growth? Add more light, add more CO2 and more nutrients.
Ramp up everything or slow it down, depends on what growth rate you want, there will be trade offs when that is done however, basically more light= more CO2= more nutrients = more work= more growth.

Regards, 
Tom Barr


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## tuvix72

Hello Tom, What a pleasure to run into you again, I miss reading your posts!



plantbrain said:


> Between simple experimentation by myself and some other failings, Ole pointed these out, I took a very different critique on the matter, this does not bode well in any likelihood.


I say this with a big grin... we were discussing this on and off since the late 90's... glad to see I haven't missed anything... we still haven't got a clue! 



> So how much ppm and difference is required for this in exogenous conditions like in aquariums, Hydrponics or???? Nice to speculate, but I've seen no evidence at all for this in aquariums.
> 
> Just because Ghori claimed to see it in a tank or two, does not imply it's what was causing the issue he had. I and others added high K+ and had low Ca++(Like most folks in the SF bay area do anyway) and found not correlation, thus this hypothesis has been falsified. This is a sure thuing, why Ghori or others saw correlation in their tanks remains unanswered however, thus they cannot conclude, whereas I can in saying high K+ does not inhibit Ca++ uptake.
> 
> At least up to 50-100ppm K+ and low Ca++ 4ppm or less.
> Hydroponic solutions typically use 200ppm + or more K+ and these can rise to 300ppm, and we still see no stunted or Ca++ inhibition. We also cannot say as aquarist without doing Ca++ tissue analysis of the treatment if in fact it's Ca++. Correlation is simply never enough when there's counter test that show no such issues.
> 
> Folks mistake Ca/K signalling pathways that are endogenous cell mediated micro/millmolar concentrations and growth/uptake. Tyhese are two very different things that have been confused.
> 
> I really do not know what ppm's is required for inhibitory effects for most of the nutrients, I suspect most are in the salt stress ranges, which are hundreds of ppm's, well above Hoagland's solution levels, which are 52ppm for P, 235 ppm for N, 210 for K+ etc...........


Well, this is one of those situations when I'm basing this 'knowledge' on what I have read. So needless to say I have no reason to stick up for someone else's opinions, but I have read this on several occasions, in particular in the agricultural sector. I have also read other studies on both sodium and manganese interactions with calcium and magnesium uptake... but I don't recall levels, it was sufficient for me at the time to understand the possibility of this situation.



> I think we are an order of magnitude less, even if we muck up by say 5x, we still are okay, even with discus and shrimp, Tonia or any wimpy plant of choice.


Agreed, our margin for error is quite generous... but I am still hesitant to throw 'balance' out the door, it just sounds a little extremist to me to do so just because light and CO2 have gained importance over the years... I need to warm up to this idea!



> As I stated earlier, all it takes is one example to disprove the stated hypothesis, I add 5ppm 3 x a week to this tank, well in excess of 5ppm total residual and I have never induced any such algae, let alone GW.


What are your other levels though? Yes I've had these levels work for me, my example was what I'd call a well balanced tank running at typical (original) EI levels with nothing more than PO4 raised to these levels... this is what kicked off the green water in this case. Be it due to the level itself or deficiency it caused in other elements, I was forced to change more than just PO4 dosing in order to sustain the level and not have problems. Hence my point of view of there being an overall balance to aim for. I don't dispute for a minute that a tank can indeed work at these levels, I just don't believe (yet) that we can dose 5ppm in a healthy planted tank (used to far less of a concentration) and expect absolutely no negative results without making other changes.



> CO2/light etc, are larger players.........and far more likely to explain differences in such results. Adding to that, light and CO2 are the most poorly measured of any parameters. So folks tend to be bias towards ppms and nutrients in their assumptions.
> 
> This is unfortunate and hopefully this will change.


Agreed. I also, as you may recall, give great importance to the maturity of a tank. There are things I can do with a mature tank that I cannot replicate in a newly setup tank, not without doing things differently. A mature tank's margin for error is greater than a new tank in my opinion and I feel at times different conclusions may be drawn based on the maturity of ones tank.

One example which to be honest somewhat surprised me, is one of my personal tanks... a 40g hex with 110W of light which a few years ago started as a typical EI tank with the addition of substrate nutrients (you know I'm a fan of that...). A couple years ago when I had to cut back on tanks and time invested in this hobby, I decided to leave the tank to it's own fate and did nothing other than topping off evaporation. No more ferts, no more root tabs, no more water changes, no substrate vacuming and the canister hasn't been touched in about a year... The HC floated to the top eventually and is now covering half the surface as a semi-emersed surface carpet and the rest of the plants are doing quite well. Growth rate has dropped obviosuly, but no algae problems or other issue... Light and CO2 are the only items I've maintained. I don't know if this is more of a thumbs up for maturity or good CO2/Light maintenance, but I'm pretty sure I could not replicate the situation on a brand new tank...



> Oh you _wise sage_ you:hihi:
> You got it and know where to look.
> 
> The entire system, that is the key, not so much looking at ppm's and micro management.
> 
> Light drives => CO2 which in turn drives nutrients, sort of obvious and simple concept, but it is used to better manage a given horticultural goal. With less light, I get higher CO2 use and light use efficiency. It is easier for me to add CO2 and places less stress on fish since there's less demand and the total ppm target is less for CO2.
> 
> This in turn means less demand for nutrients, so my range for non limiting ppm is much larger, as if I do limit something, the resulting intensity is also correspondingly less. So there's just a mild effect, not disaster:icon_idea
> If you limit light and then limit CO2, now you have an extremely robust method: non CO2. Many non CO2 planted tanks have high PO4(several ppm) and low N and they persist for months without change.
> 
> I think aquarist are better off looking at these other factors and how they tie together to explain things more and to look at better ways to manage algae, rates of plant growth, various problems they encounter.
> 
> We spent a lot of time playing with nutrients, suggesting ranges, adding just enough etc, but gave much less consideration to light. Why not limit things with light? Why not add just enough light??? Why not squeeze every bit of growth out the plants with the lower light? Are we not wasting light/energy/electric bills using more than we need for nice growth/good rates of growth??


Well we were discussing this stuff back in the day too... Most ADA tanks have always been low-medium light setups in reality (excluding the central peak) and most of the plants are slow to moderate growing ones. I've always favored lower light setups as I feel I have had the best growth in terms of quality with these. And today I do find myself helping novices who unfortunately walk out of a store with way more light than they will ever want to deal with... it seems that just because more efficient light is available and cheaper than it once was, stores are pushing such fixtures without much reason... sorry I'm straying from the topic now...



> Algae are not limited by CO2/nutrients, but what about light?
> That's the only parameter I can think of where they might be.
> 
> I've long heard that adding non limiting nutrients is "wasteful", but why is this not applied to light? Electric cost a lot more than any nutrient excess and adding more light stresses CO2 management/addition, nutrients, etc.
> 
> This gets to very fundamental issue with algae, management and rates that we want/have as goals. Nutrients? Not very much, it's more the tail wagging the dog there.


Agreed... but again, I need to wrap my head around this concept a little more... I have to think back at some of my past setups and look through the log books a little, always good to do when new concepts are considered, facts are always facts, we just interprit them differently... :biggrin:

Regards,
Giancarlo Podio


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