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Re: [APD] NO3 limits in planted tanks

Thank you Tom!
You are really putting some scientific foundations under this hobby. And, the last test kit I had said, in the instructions, NO3 must be kept at zero - that was about 5 years ago.

This does raise a couple of questions, at the least. One is, does this reduce the necessity for weekly 50% water changes? I would expect that it would mean that we can be at least a bit more relaxed about that. And, the second is, how does this affect the goals we aim for in fertilizing? Still 10-20 ppm NO3 and 1 -2 ppm PO4? I would expect that one would do better to try for the top end of those ranges or even a bit higher? Or, perhaps just forget the limits and let the plants decide when you have enough, once you are above the bottom limit?

Have you any plans to research light needs further? Like developing a formula for watts per square meter per meter depth of water? (watts/meter cubed)

On Tuesday, June 14, 2005, at 10:08 AM, Thomas Barr wrote:

I found out that NO3 levels over 120ppm do NOT cause nor induce algae in any way.
That said, it does cause certain plant species to melt (but not Crypts as often erronously stated in past literature and repeated anecdotal comments across the web).
I found the LD 50 for NO3 and Amano shrimp.
(LD 50-> the level at which 50% of the organism is killed occurs over a given exposure time, often used in toxicology protocols)

3 day exposure at 100+ppm will cause them to act sluggish and slowly die off.
Fish were unaffected but showed some signs of stress.
Some plants showed signs of slower growth or leaf melt.

NO3 was from purely KNO3 inorganic inputs.

This again is interesting because at 100ppm of NO3 I did see some negative plant response(inhibition/toxicity) but no algae responses.

It seems that negative plant responses are more of an issue with the upper ranges of the macro nutrients rather than any issue of inducing algae.

I have still yet to have found any PO4 that causes plant inhibition.

Still, given these extremely high nutrient levels, I think it's very safe to say that excess nutrients over an extremely wide range causes no algae blooms.

Perhaps the rest of the folks on the list can explain this to other folks that still suggest algae or plants outcompete eachother for these resources(impossible obviously when the levels are 5ppm PO4/100ppm NO3---all in bioavailable inorganic forms), or that excess nutrients induces algae(other than NH4/unstable CO2) that these issues are simply not true.This will help stop myths that have long been established and further the hobby.

I tested high levels of Trace elements a few months ago and found that using SeaChem's Flourish at 100 milliliters/per 100 liters of tank (or 10mls per liter of tankl!!) did not cause any shrimp toxicity nor any negative plant response over a 7 day time frame. The water was very dark during this time from all the trace elements.

Again, this clearly shows that excess, or high levels of Fe and other trace elements such copper have no adverse effects or impacts on flora or fauna.

So I still do not know what PO4 or trace element level is toxic and causes plant inhibition.
But..........it's extremely unlikely someone wilkl make their water tea colored with trace elemtns or add more than 10 ppm of PO4.

Therefore the usable range of all needed plant nutrients is enormous without any negative flora or fauna impacts.
The issue is really one of nutrient levels that are too low, rather than too high.

There are limits, but they are so high that it's only in the context of a purposeful extreme over dosing that this occurs, far beyond normal hobby error.

Tom Barr


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