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>Neil Frank wrote:
>>...Maybe urea is like time released ammonium. This might be a great
>>N in a heavily planted tank.... and might prove to be reasonably safe at
>>concentrations of up to a few ppm.....
>Be vary cautious in the addition of urea. In small doses, it seems to do
>no harm, and I have seen growth responses in nitrogen deficient plants.
>But in larger doses, it kills Daphnia and causes huge green water
>outbreaks. (I tried 43 ppm!) It doesn't seem to benefit the plants much
>in larger doses, and the algae takeovers can cause a lot of damage to the
>plants. It is definitely not a form of nitrogen that you can put a big
>reserve supply in the water. An equivalent dosage of nitrate nitorgen
>would be 62 ppm nitrate, and that doesn't seem to harm anything.
Paul, can you please clarify. 62 ppm nitrate is equivalent to what? Recall
I only said a few ppm urea. This is coming from a person that only feels
comfortable with 0.05ppm of NH4 and 0.1ppm of P. I was figuring that a
concentration of urea > .05 should be OK. Question is how much higher than
.05 (.1?, .5?, 1ppm?) . This all depends on how quickly it goes to NH4 and
how quickly do the plants suck up the NH4. With a true slow release, there
can be no residual NH4. BTW, I was not planning to dump in 43ppm!
Neil Frank / Aquarian Subjects
Interesting old books and magazines (but most plant books are already gone)