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Clay as bacterial substrate?

In all the discussions I have seen about clays and laterites, the CEC is
presumed to be the only relevant effect. What about clay particles being a
substrate for bacteria? Could this also affect nutrient processing within
the aquarium?

Plant people seem to put less of an emphasis on bacteria, because the
plants take care of nitrogenous waste for us (for the most part). But
outside the plant world, aquarists focus on surface area of their
filtration media because the nitrifying bacteria need a place to attach to.
Hence the sintered glass, the fluidized bed silica reactors, the activated
charcoal, the ceramic pellets and the lava rock. Clay particles have lots
of surface area. Does presence of clay in the substrate increase bacterial

 Maybe we don't need the nitrifying bacteria for oxidation of ammonia and
nitrite, but maybe we do need them, or other substrate-anchored bacteria,
for processing of other nutrients. I don't know what form the phosphorus in
fish waste is, nor what form plants prefer it in, but might bacteria play a
role in any necessary conversion? Many bacteria produce siderophores which
chelate iron into a complex which many plants can exploit. K+, Mg2+ and
NH4+ we don't need bacterial help with, of course, but perhaps there are
other micronutrients which bacteria can produce or process.

Michael Schmidt
California State University, San Marcos
San Marcos, CA