yes this was about GDA,
Ok. You might want to edit your original post - GSA is mentioned several times when it should have been GDA, and that might confuse people right from the start in an experimental log.
So now let's have some real fun.
i also learned that extra K+ increase the uptake of nitrogen, this is also confirmed by the MCI, they don't recommend having more K+ because they said it will drop the NO3 levels and cause cynobacteria.
Yes it can. But do you also know why this occurs?
In the following example I will refer to a plant as if it could think. It doesn't have a brain of course, just a complex chemical regulatory system; but it's easier and more entertaining to describe things as if it were intelligent.
Suppose we have a tank where potassium is almost exactly what is actually required. And then we increase it. Even if the plant didn't need more, but especially if it did, these are happy times from the plant's point of view. It would rather have a bit too much around, than just enough, or too little.
But it also realizes that it's in an environment that can change. If a nutrient can increase suddenly, then it's also likely that a nutrient can decrease suddenly too. How best to cope with that?
A plant can't store potassium, so if it should decrease, there's no way it can prepare for that in advance.
What if another nutrient were to decrease, like nitrate? The plant can store that, quite a bit of it in fact. And it goes about doing so. So even if the nitrate were to drop, it can still continue to take advantage of nice potassium levels, for as long as they might be around, and as long as its nitrate stores permit. It's prepared itself for future lean times in the best way possible.
Here is where we might notice something is wrong. Perhaps BGA or some other algae has appeared. Test kits show nitrates have crashed. Was increasing potassium the wrong thing to do? The algae says it was, MCI says it was, so we hastily reverse the potassium increase. Algae goes away, everything returns to normal, and we swear off excess potassium in the future.
And this is exactly the wrong thing to do. We only stepped halfway through the door, then panicked and retreated before seeing what was on the other side.
Instead, we could have increased nitrate. The plants' capacity for nitrate storage is not infinite. In a week or two, they will fill up, and stop removing it at such a ridiculous rate. At which point we can stop dosing extra nitrate. The plants are happy because the extra potassium is still around, they're fat with plenty of stored nitrates, and not so worried about possible future lean times in general - so they go about putting these nutrients to good use, and growing big and healthy.
Perhaps more importantly, we no longer have to worry about dosing too much potassium. The plants are already full. Increase the potassium further, and the plants will still manage to squeeze a little more nitrate into storage, but there won't be another major nitrate crash. Only a dip, which quickly passes and is usually unnoticed.
With heavy dosing schemes like standard EI, there's so much extra nitrate and potassium around at all times, nitrate crashes are rare. It's only with leaner dosing that crashes become a common issue.
And when such a crash occurs, we may easily be fooled into blaming extra potassium. When in fact the real problem was our failure to anticipate and respond to the plants' needs, and dose the extra nitrate they want.
All nutrients are interrelated. Increasing dosage of one nutrient increases uptake of all others, and if any one of the others was originally only sufficient, then it will become deficient. Or if any one was originally only sufficient, then decreased into deficiency, then by reducing uptake, it may eliminate a deficiency in another nutrient. The nitrate/potassium relationship in particular is notorious only because a small change in potassium can cause a much larger change in nitrate.
Consequently, it's extremely difficult to isolate the effect of any one nutrient in any lean dosing scheme.
In such a situation, let's say I want to bump up a particular nutrient and see what happens. If there is ANY chance whatsoever this will cause increased uptake in any other nutrient to the point of deficiency, I will bump up ALL other nutrients by a lesser amount simultaneously, in an attempt to hopefully prevent this from happening.
And when doing algae tests, this is particularly important. Because deficiencies in the water column are actually a valid form of algae control. Oooo, yep, I went there.
Do you remember PMDD? It severely limited phosphorus, causing actual competition for it in the water column between plants and algae. Now in a fair fight, the algae will always win that competition. But plants can access nutrients in the substrate that algae cannot. So it worked often enough that it developed a following. It did not, however, work for everyone. I only said deficiency was a valid form of algae control, not a good one!
Mr. Rubilar of MCI fame has incredible skills, beautiful tanks, and has run extensive tests. But these tests were done with a lean dosing system which, due to all the reasons I've detailed above, would have put him at a severe disadvantage for understanding what's really going on with every change. So if you take a fragment of MCI and apply it to another dosing system in an attempt to improve it, it may not work at all. Or it may work, but not for the reason Mr. Rubilar claims, regardless of whether his reason is valid within the MCI system or not.
One more example. I'll keep this one brief:
Day 1 KNO3 and PO4 added to water (no GSA)
Day 2 (No GSA)
Day 3 (KNO3 added but no PO4 added)
on Day 3 when i came home you can start to see GSA starting to appear on bottom of the glass.
I've done this too, and seen the same result. But it was NOT a phosphate deficiency, at least not really.
I broke out well calibrated test kits. Phosphate was at 30ppm! Despite that, adding more phosphate got rid of some, but not all, of the GSA. The bigger issue was discovered with nitrates, which were at 120ppm! Fixing the nitrates completely fixed the algae, without any need for additional phosphate.
Proof of an optimal nitrate/phosphate ratio, like the Redfield? No. At those elevated levels, my N:P ratio was 4:1, and it wasn't working. But 20ppm nitrate and 5ppm phosphate is the same 4:1 ratio, and that works just fine. It's more complex than just levels and ratios.
And I'm going bold now, because this is the most important part; I want to make sure everyone sees this, even if they're skimming my post at this point.
None of this is meant as a direct critique of your experiments, or to say I don't believe your results. In fact, I don't really believe ANYONE unless I do exactly as you're doing, and test test test - which is GOOD! And I certainly don't want YOUR thread to turn into a debate about any of MY statements; I'm certain few will fully agree with everything I've said, so please folks, let's just leave it at that. The intent of all this is only a demonstration of just how complex and misleading the aquatic environment can be, in order to serve as inspiration and possible guidance for additional experiments. If I'm wrong on something, then that makes it an even better demonstration.