Bivalves (clams and mussels) are easily dispensed with as far as their usefulness in freshwater aquaria goes: don’t bother. Putting aside the fact that many of the species sold as freshwater mussels come from temperate zone waters and won’t live long in a tropical tank anyway, none of the clams or mussels in the trade feeds on anything other than plankton. So unless you are prepared to use a turkey baster or pipette to squeeze in portions of filter-feeder food (obtainable from stores catering to marine aquarists), any clam or mussel placed in a freshwater tank will die. Admittedly, it might take weeks for them to die, but die they will, through simple starvation. Contrary to what some retailers might suggest, clams and mussels cannot simply survive on the algae floating about the water, unless your aquarium water is so algae-laden it is the colour of pea soup! Nor can they ‘scavenger’ in the not clearly identified sort of way other retailers might suggest. Clams and mussels lack mouthparts and cannot chew up food or graze on algae. A happy clam is one that has dig itself into the substrate, so even in the best case scenario these animals don’t put on much of a show, and should such a beast die hidden away in the sand, its decomposing body can create a nasty pocket of anaerobic decay as well as an extra load on the biological filter.
