filterless plant tank.
I just set up my freshwater tank again after a long hiatus and am trying
out the filterless approach. I toyed with the idea for a few months before
and even ran my 100 on no filter for about 1 1/2 months. However, the fish
load was extremely low and the time of the setup wasn't long enough to
really get any real data. I don't feel the plenum is essential or even
beneficial; most reefkeepers have moved away from the idea of a plenum but
are instead using live sand. In freshwater tanks, an analogous situation
occurs with the Malaysian trumpet snails and fine grained Texblast gravel.
Anyway, with a sufficiently deep sand layer and enough sandstirrers, the
anoxic regions necessary for dentrification should occur. To help avoid
anaerobic conditions, however, it's a good idea to have good water motion at
the surface of the sand bed (via a small powerhead). Anyway, in about 6
months I'll tell you how it turns out...