i originally got them to clean up the mess from my dragon goby in a small 10g, after i rehomed that fish, i put them in my 55, where they stayed quite happy till i recently got the jack dempseys, who liked to bite at their eye stalks, so i put them in my 8 foot tank with the oscars, and so far they have been in there for a few months, and they are all still alive, the oscars dont care about them in the least. and all things add to bioload, but i dont think even 50 snails would have more bioload than one of the large plecos