Originally Posted by Blaxicanlatino
I was thinking of putting sand in my tank as well but then i thought.... i was going to using malaysion trumpet snails in my tank. So the snails will will stir the sand as well as help eat loose debris in the tank. BUT wouldnt the snails also defecate under the sand? How would i clean the waste if its buried in the sand and wouldnt that pollute the tank?
In planted aquaria the substrate, whether sand, gravel or pebbles, is rich in organic material (waste, added fertilizers if you add them) and naturally contains bacteria that break down the organics into nutrients that can be used by the plants. The bacteria quickly use up the oxygen that is in the water permeating the substrate, and the substrate becomes anaerobic. At this point, different bacteria form, those that either do not use much oxygen or can manufacture their own. These anaerobic bacteria release toxic gases like hydrogen sulphide which can cause plant roots to rot, damage fish health, and encourage algae. But these conditions also prevent the binding of nutrients with oxygen molecules, and as the bacteria use the nitrates, nitrogen gas is released, an important plant nutrient. At the same time, healthy plant roots release oxygen into the substrate. So there is a lot of activity down there.
As long as the substrate is not too fine and compact, the combination of slow-moving water currents and the release of oxygen by the plant roots should prevent the majority of the substrate from becoming anaerobic. Malaysian livebearing snails assist in this process by burrowing through the substrate. Anaerobic patches do occur in denser areas, but being small (normally) they will not produce large amounts of toxic gasses but still allow nutrients to be available to the plants.
In aquaria without rooted polants, the same biological action occurs, except obviously there are no plant roots to add oxygen; but the general process is similar. All waste is broken down by bacteria, whether under water or on land. The aim in a closed system like an aquarium is not to have more than what can be handled safely. Thnis is one (and only one) of the problems associated with too great a biomass in a tank. But in a tank that is biologically balanced and has regular maintenance (weekly partial water changes with substrate vacuuming) this will never be a problem.