NO3 and PO4 in Takashi Amano Aquaria

["John T. Fitch" <JTFitch at fitchfamily_com>]

In an article on "Driftwood in the Nature Aquarium" (TAG, Vol. 16, No. 2,
April-June 2003), Takashi Amano provides nutrient levels for two example
aquaria. On pages 4 and 8, the NO3 level is given as <1 mg/l in one case
and 1 mg/l in the other.  In both tanks the PO4 level is given as 0 mg/l.

My understanding is that the macro nutrients, N, P, and K, are all
required for plant growth. The recommended level for NO3 is 5-10 mg/l and
for PO4, 0.5-1.0 mg/l.  I've also read that letting either level fall to
zero is an invitation for an algae outbreak.

I hope someone will explain how the Amano tanks can be successful at the
levels given. I thought, at first, that possibly his elaborate substrate
with something like seven ingredients might be the answer. But then I
realized that many, if not most, of the plants shown in the illustration
on page 4 are growing on rocks or driftwood and must be deriving their
nutrition from the water.

There are two further measurements given, which I hope someone will
explain. They are TH of 20-40 mg/l and COD of 4-6 mg/l.  Thanks.

John T. Fitch
E-mail: JTFitch at FitchFamily_com
Web Site: www.fitchfamily.com/aquarium.html