Plenums create an anaerobic area where nitrate can be broken down into nitrogen
gas...correct? I know some african cichlid keepers who use very deep sand beds for
exactly this purpose, and never have measureable nitrates.

LeighMo wrote:

I am starting my
first tropical freshwater aquarium and I have built a plenum found at
www.garf.org which is primarily for growing reef.

Plenums are used for sal****er tanks. There's no point in using them in
freshwater.

You can still have a fairly self-contained ecosystem, if you want. Try reading
Diana Walstead's "Ecology of the Planted Aquarium."

Leigh

http://www.fortunecity.com/lavender/halloween/881/