The concept and logic behind a non limiting control for nutrients, EI's basic premise

Tom Barr

Staff member
Jan 23, 2005
It plant research test, Hoagland's solutions are often used as a non limiting reference for plant nutrients and a pure DI water source is most often the most possible limiting opposite. Thus when looking at plant nutrients, everything else will fall somewhere in between these two references.

Makes sense?

EI is simply a version to maintain and keep a non limiting nutrient solution for aquatic plants, fish and shrimp etc. Nothing more. This assumes that even at high light and rich CO2, the nutrients will not be limited.

Unlike Hoalgand's, we do not use NH4, due to toxic side effects mostly, but a little comes in from fish waste and small amounts can be added, but really do not help plants much relaltive to enriching the tank with CO2, adding more light etc.

Thus when the nutrients are non limiting, they are independent.
Other factors will not be influenced by them.

So you can now test CO2, without any interference from say PO4, or NO3 which might be limiting and causing less CO2 demand.

While we can easily rule out nutrient factors rather easily with EI, the same cannot be said for CO2. Light can be measured and compared easily with a 200$ meter for PAR(Apogee etc). But CO2 is a much tougher issue.

Isolating CO2 is very easy can make the light independent(simply measure it with a meter and compare with well growing plant examples), and more importantly..........make the nutrients independent.

Thus the only dependent variable is CO2.

There's things like water changes, filter cleaning, pruning, and current, these are part of the issues as well, but as far as nutrients/CO2 and light, the EI method allows independence from nutrients.

This is good for experiments, research, isolating the issues aquarist might have etc. It's a simple easy effective tool to look at CO2.

Folks hear me carry on about CO2. There's a good reason and this is why.
I have several aquariums and they all have the same exact fertilizers and water changes etc done to them. Some variations in the plants species and biomass, but..........the ferts are exactly the same as is the sediment.

Lighting can be adjusted to be the same in each case since they are suspended and raising the lights up or down can easily dial in the same PAR value.

So why might two or more tanks be so different? CO2.

To test this, we can simply adjust the CO2 valve to add more/less and use the plants we suspect are having CO2 issues, and lo and behold............they exhibit the same patterns so many claim are Ca++ deficiency(stunted tips in some species, but not others). We adjust the CO2 back up, the growth issue goes away. We reduce the CO2 and the pattern appears once again. After 3-4 times, we can be sure that it is a CO2 issue......................

Next we chose the theory that some on the web like to claim proves their point.
We use the higher CO2 value and a healthy tank to start with where the plants are doing fine. We add excess K+, say to 50ppm. Then we keep adding it as K2SO4.

If no stunted tips appear, then the test shows that it cannot possibly be excess K+ causing those folk's issues and is much more likely, that their CO2 was not independent. Perhaps adding more K+ increased their CO2 demand and they did not account for it.

Only by ensuring my CO2 was correct and independent before hand, can I confirm it was a CO2. Many on line will simply insist their CO2 is "perfect", citing a drop checker, or a pH etc. These are indirect test, the issue we are testing is in fact, the plant itself. I chose to use the plant as a test kit rather than a pH or a drop checker, both of which hardly ensure anything other than the assumptions that go with them.

I think many simply think they are a lot more sure than they really are, do not believe everything you think. Go back and try and confirm what you think is true. See if you can induce the growth using CO2 and that alone.

Chances should be rather easy.

Also, it warrants a second look if someone comes along and has high K+ and no issues with that same plant, you need to go back and figure out what caused it. Not just tell everyone that by limiting K+, now you prevented Ca++ deficiency. You did not and you did not check the alternatives, even when other folks mentioned CO2 etc confounding your results and conclusions..............

Now if you want to Bull manure yourself...........that's your own deal, but do not tell other folks that you are right and poo poo personally on others or a method with such (lack of) logic.

Such claims do not address the facts that falsify your claim. However, the ones I suggested, rule out nutrients, light and CO2 effectively. Still, the suggestions I've made, still.........does not rule out things like current, filter cleaning, initial state of the aquarium, biomass, specific plant species etc. Those need addressed well also.

This same approach applies to fish toxicity, shrimp etc, temps, PO4, NO3, NH4.........etc. The logic is the same. You make a hypothesis and then try and falsify it through testing. Then you go back and try and confirm it.

Some on the web wanna just speculate with a little correlation and claim these grand theories................about cause etc..........but have not demonstrated whether they are causal or not. That's fast, that's easy, there's no stunting plants on purpose or any knowingly harmful things done to the tank, but they are often wrong most of the time as to why and to the cause. That does not help, enhance or improve this hobby. It does enhance and reinforce the myths that are wide spread already.

As far as I am aware, EI is about the only nutrient dosing method I know of for aquariums that's non limiting and does not assume algae will bloom due to excess water column nutrients. Those that claim that nutrients induce algae, need to address why my tanks as well as others lack algae that dose EI.

Obviously, they cannot, so they hedge their logic and play semantics instead(irrational, cannot accept it based on logic). Or they end up agreeing(rational, can see the logic and then an intense look for alternatives to algae blooms- this is true curiosity, not a big ego and hard head).

This issue has bothered many that claim excess/non limiting = bad or induces algae, so they have attacked it. Yet..........even over a decade later, I've yet to see one person demonstrate any reason why my tanks not have algae even in light of excess/non limiting nutrients.

So it's stood the test of time, the test of logic and the basic test done in research.
I suppose if you cannot win on the merits of logic alone, you bad mouth and keep saying the lies that you have told yourself many times to the point you believe what you think.

Misinformation, trying to distract etc........same crap that politicians pull on the public are done many times also. Marketing as well by companies wanting to sell you something for every myth:cool:

You know the deal. Be smarter than that and use common sense.
Often, our common sense is about all we have to work with.

Tom Barr