The reason your LFS gets away with the high number of feeders in their tank is because: 1) they probably get rid of (sell?) them before they have a problem with them 2) they probably do a 100% (or close to it!) water change everyday (We did on our feeder tanks when I worked at a fish store! We would run a garden hose to the tank while a 500 GPH Beckett pump was running and let them both run for an hour or so every single morning!) 3) they NEVER feed the feeders any food! This keeps the ammonia to a minimum! Are you NEVER going to feed your feeders? Even after a month? As they say: "Garbage in = Garbage out"! Poor quality feeders do not do your fish any good!