Stable Tanks need little Fertilizing?


Lifetime Charter Member
Lifetime Member
Jan 24, 2005
Sacramento, CA
Dosing Ferts for Someone Who Can't On Weekends - Science of Aquatic Fertilizing - Aquatic Plant Central is a post on another forum that claims you can achieve a "stable tank", then it doesn't matter if you skip fertilizing for several days, and you only need tiny amounts of fertilizers to keep the tank going, algae free. This isn't something I have heard discussed before, that I can recall, and it goes against everything I think I know about fertilizing. Does anyone have any experience trying this "method"?

Tom Barr

Staff member
Jan 23, 2005
It may be useful to ask a good question first:

What happens when you stop adding ferts and have an over grown/stable tank?
What is meant by a "stable tank"?

To the rate of plant growth that is?

It slows down.

What happens if you have less light?

It slows down.

What happens if you have less CO2?

It slows down.

It's not just ferts Vaughn, it's all 3.

The tank also might have plenty of reserves in the plants, or the roots, so a few days of no ferts might be fine.

You also might have enough organic matter built up in the sediment, much like an ADA aqua soil sediment that water column ferts are not needed.

If the tank is well shaded due to over growth, you also get less algae and issues, same deal with a non CO2 planted tank once it grows in.

Some tanks have more fish, they have a decent input of ferts from the fish waste, at least enough to prevent critical nutrient deficiencies.

So what would favor this senario you mention?

1. Less light first(is anyone on APC even bother to measure light?)
2. Less CO2/none at all/Excel(careful precise CO2 measurements? Think that this influences growth.nutrient demand?))
3. Rich sediment(how are they testing.accounting for this one I wonder?)
4. Low nutrient tolerant plants, some are much tougher under nutrient limiting conditions(say Anubias vs Eustralis)
5. Fish load/feeding(folks can feed far different than other folks)
6. Plant biomass differences
7. Temperature(cooler tanks have slower growth rates)

BTW, AF has hardly added any ferts to the 120 cm tank for a month, but it's loaded with sediment ferts. You can also reduce water changes without ill effects. But the tank does look nicer if you do the water changes and keep up on trimming and care. Folks get lazy is all.

But that's fine also, there's a trade off there.
It's not that it's some revelation.........or something like many seem to assume.

Not hardly.

You let things go for a bit and then hack and do some work to whip it back into shape again. If that's your goal, then use less light, ADA AS, cooler temps, higher fish loads, less nutrient demanding plant species, Excel only, etc.
Then you will have fewer issues and it'll be even easier to let things go.

I garden sometimes, but then I get side tracked, many do.
If you like a nice ADA style tank, trimming and gardening and ferts, water changes are part of the game.

If you seek no dosing, less work, more patience, no water changes at all, want to grow the tank in nicely and then have it be stable, why the hell not just go a non CO2 method or use Excel/low light?

All this stuff is already well known.
DW makes a good case for this in her book.
The other parameters influence growth and can do so dramatically or with varying degrees of intensity.

You need a starting point and light is the first one and then you go from there and look for CO2, then the relationship between light/CO2, then you go to nutrients ands WHERE the nutrients are and at what rates they are being added and what are all their sources, not just merely inorganic ferts and what you can measure with a 10 $ test kit and only in the water column.

You need to look at the entire system more carefully.
Where the nutrients are coming from, what determines the rates and cycling of the nutrients etc.

You end up make errors otherwise.

Tom Barr


Prolific Poster
Nov 12, 2005
(continued from permalink)

It is all about imitating ADA’s system.
It is limiting plants growth with light, not by low PO4 in water column - in ADA's system they are not limited because have nutrients in substrate.
They try to imitate it forgetting to place nutrients in some other place :)
I understand this system as keeping very low nutrients levels in water you really make slower and less severe algae outbreaks in case of imbalance. In case of algae bloom greatly increasing WC you do limiting algae, but not plants as they have roots and can steel feed from substrate.
Algae dyes off quickly, plants not harmed.
You have to do less WC, without difficulties of feeding plants dosing in water at the end of this period (this feeds algae too!).


I am interested in PO4:NO3 ratio because of a substrate - what is exhausted faster in ADA AS + PS - N or P. This may help to formulate DIY mixture. For example if we need more P pool we can try to use non soluble “Rock phosphate” (apatite). :)

I also never forget about another ratio from RR - C:p.

Secondly, I can't get why when we care of PO4:NO3 ratio we do not care of CO2 assimilation?

At lower CO2 concentrations Rubisco needs more N. It is clear.
So if we dose 1:5 we do not have enough N for CO2 fluctuations, especially in long run and with lean substrate.
Sure we can simply dose more 1:5 mixture, but than we will have much more algae biomasss when problems with CO2 will arise. Isn't that?
Isn't that logical to keep less PO4 in water and more in substrate to make system more User friendly? (we know plats prefer getting P from substrate, even stem plants)

So why we should keep so much PO4 in water column and shift ratio to P ?
To have more algae in case of CO2 drop doubling it with less Rubisco activation?

Maybe this is why we see threads like THIS looking for something more stable and User friendly and there are not much EI funs with east-method or without pH-controller, esp. dosing full EI ?

Or this is why we see folks shifting to ADA's system, making a *huge leap* in overall tank quality and stability, and do not care anymore of any other methods/systems/routings?
And CO2 is OK without dropcheker with Reference solution or pH-controllers, easily.
Maybe we should look more carefully at ADA's system as a whole and ask yourself Why everything is OK without so hard monitoring of CO2 supply?

Evidently we should look for more factors involved managing CO2 assimilation by plants, not just *monitoring* CO2 supply.

I see such factors are noon spike, and more N in water column as insurance.
Both targeted for better assimilation of CO2 which we Have with atomizer, instead of increasing CO2 concentration or harder monitoring it.

We already know (thanks to PJAN) ADA’s noon spike gives less nutrients demand (more internal buffer), so less demand for CO2.
We can have less CO2 concentration without starving plants on carbon. This is very good.

One more interesting factor is that noon spike can also greatly improve Rubisco activation (at least for terrestrial plants it is known to be true).

As we could see in Ole’s data which I already mentioned somehow no detrimental effect on Rubisco state when P is limited.
This is because of better Rubisco state – more N pool, more Rubisco activated, more CO2 assimilation at *lower* concentrations.
And very bed situation when N limited instead of P.
This is not the only paper which says this. It is known that having lots of N we can limit plants growth limiting P, without sacrificing Rubisco state.
This alltogether allows to keep much less P in water to have less algae biomass *in case of problems*.

Some years ago you stick to ADA AS, so this is not EI any more (at least your 180gal tank).
If you couple this with noon spike lighting you will have complete ADA's system.
Not EI at all or it’s leaner twin “invention” PPS-pro.

Quite often folks try to use some elements of ADA’s system, instead of putting it all together – water changes + lean water column dosing + rich substrate + noon spike lighting.

I am trying to understand HOW it works and WHY it is so stable.
Why everybody tried it (with ADA products or without) gets excellent results and never asking why it works anymore - they simply use it.
And they do not interested in EI or PPS-pro etc. brands of just one of the elements used long time ago without this “labels”.

Things I mentioned here and others makes me think I can grasp why.
Sure I can’t beat you in argumenting and scientific background and can have some mistakes, but not in general understaning…


Tom Barr

Staff member
Jan 23, 2005
Rubisco is not a P sensitive enzyme for an obvious reason: it has less P requirements and most plants are well adapted to low P, if you have no N, you are in serious trouble however.

Low P will have much less impact on growth than will low N.

I do not think there is any less issue or more with algae if you keep things lean or not, because none of these idiot's know a thing about algae or how to measure, test and show that they are really limiting algae at all.

I get sick of them claiming this crap to tell the truth.
They make claims and do not support them.

Sounds nice, but it's not true.

Inducing algae is how you see and learn more about it.
It's not the least bit true in research data on tropical or subtropical lakes.

The research suggest there's NO PATTERN.
See Bachmann's reference for proof, not speculation.
462 lakes where measured and considered in the study.

Algae limitation studies from Ulrich also shown that P limitation was been resolution of even the best instruments.

Now if they cannot show it, how the heck can a hobbyists?
Get real.
I cannot do it either.

So how can they even say this?
The "power of belief" and/or ignorance?

I've already mentioned this many times over the years, so the info is there and available to hobbyists.

Naman, you are very correct about C and N and P linked together(light as well).
If you limit P a great deal, then you will reduce CO2 demand, and N.
Likewise if you strongly limit N, you also limit CO2 and P demand.

Plants have a good amount of storage of N and P, but not C really.
It's just needed in too large amounts in small weedy plants.
Aponogetons have extra etc, but most plants do not.

Yes, you need more Rubsico at lower CO2.
So a plant in a non CO2 tank has more Rubisco per unit area/DW etc than that of one in a CO2 enriched planted tank.

So you will also see more N per unit dry weight in the non CO2 plants than those of the CO2 enriched system.

Now if you consider this, then the ratio of N goes down in these plants, so a ratio of 4:1 N:p is fine whereas in a non CO2 tank, 10:1 might be better.

ADA also started adding PO4 to the liquid ferts after I started suggesting this back in 1997. SeaChem and others had been as well.

As far as ADA vs EI etc, the real issue is consistency. If you add ferts to the sediment and lean ferts to the water column vs rich ferts, to the water column, you get the similar results...if you are consistent.

Most of us are human.

So try ADA Sediments + EI.
Then you have the best of both worlds.

Not one or the other.

Sediment ferts are easy.
That is why ADA system is so good, it's not too much issue to mess with it, folks used soils for many years with good results also.

But telling folks to do water changes 2-3x a week for the first 1-2 months would help improve things there as well.
Also, larger grain sizes vs mud also helps.

So there are reasons why it works well, not some miracle.

As far as lighting, you can simply grow plants with low light without a noon day spike as well, and they do nicely.

If you drive the tank faster all day, well, then it's a high light tank and needs more CO2 etc.

But nothing stated suggest algae are ever limited in either tank.
There's just no such evidence.

EI is just a concept, using water changes to flush, ADA uses it as well but does not justify or use empirical data. These where both independent.

Using just the sediments, nothing I've said has suggested adding ferts there would hurt. So it's using ADA's sediments, I can use other things, like sand + mud.
But ADA's looks nice and easily to handle.

I like one homogenous material, not Powersand etc.

ever asking why it works anymore - they simply use it.

Yes, that is bothersome and disturbing, the faith based approach to plants:)

I think you need to really consider the effects of rates of growth, time of lighting and they interact together.

The less light= less CO2 demand.
That plays a massive role in algae.

Stable CO2 levels allows good production of plant biomass.
the PO4/NO3 are not that limiting , they are fairly rich and always available, if not by the water column, then by the sediment.

This way you benefit from both rather than one or the other.
Aquatic plants are opportunist.

So the big picture should make sense to you as well.

Lower light overall
Less CO2 demand
Moderate growth rates(less work)
Less N and P demand (allowing for translocation if too lean in the water column)

If you have high light(typical american tank)
Higher CO2
Higher growth rates
higher N and P,

Which is more likely to crash or be less table?

Clearly the tank with high light.
It all starts with using less light.

How did you think Amano figured that out?
He uses lower light, look back and ask him yourself.

The higher lighting is something he's added in the last decade or so to amplify and have more growth, color density etc

And that's also when he realized he has to add more water column ferts(N and P), Green brighty "Light" and "Shade".

Tom Barr