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Of Phosphates and Nitrates



Hi fellow aquarists,

Some enlightened folks have really opened up a door to me during the recent
discussions of actually adding Nitrates to the tank (in the form of the PMDD
regime) to enable plants to fully utilise the phosphates as phosphates in
nature are a short term nutrient and tend to be hoarded by plants. This
should be able to counter the growth of algae, as hypothesised by Paul Sears
and Kevin Conlin in their paper, "Control of Algae in planted Aquaria".

Few questions:
1. Nitrates and phosphates usually go hand in hand inducing heavy algal
growth. Supposing we manage to get rid of phosphates in the aquarium but
Nitrates are still present. Will Nitrates alone be sufficient for algae to
grow? Which is a better nutrient for algal growth? Is it Phosphate, or
Nitrate, or are both needed?

2. I understand some plants are poor utilisers of Nitrates (can't name any
exaples though. Enlightened folks, please help :) ). Will it mean that if I
add more nitrates to an aquarium using alot of these plants, there will be
little net positive effect and we will actually be worse off in this case,
due to increased nitrates in the nitrogen cycle?

3. Supposing the regime as prescribed by Paul and Kevin works, does it mean
that I can do away with the bi-weekly water changes and just change water
only when phosphates go out of control?

4. Will this regime be actually superior to the traditional regime as
prescribed by Dupla? (i.e. no nitrates in the fertilliser at all!) I do
understand that this regime is a lot cheaper compared to sticking to Dupla's.

5. Instead of adding Nitrates, will it be just sufficient to increase the
feeding of my fish (relying on the extra Nitrates produced.) But I also
understand that phosphates will no doubt, increase. Does anyone know the
proportion of increase in Nitrates as compared to Phosphates in an aquarium?
(e.g. will Nitrates increase twice as much as Phosphates, etc.)

I do hope that the scope of the Phophate-Nitrate debate could be widened
through these few points and folks with experience could share them with the
rest of us :), because Paul and Kevin's theory will really revolutionise
things if it is indeed true (read no more water changes?).





Calvin Chin