I have to take my nano skimmer out every 7-10 days to clean out the pump that gets so easily clogged. Once cleaned and rinsed then returned to the tank it isn't 2 days later that its covered with diatoms. From the tap water I'm sure. But fear not!! My Mexican Turbo is ever vigilant! In just on day he'll have it looking brand new clean as a whistle He's now 2yrs in my tank! Personally I'll take a snail over a crab any day. Much more trust worthy and do a better job cleaning up.