I use it just for filtration and something to place activated carbon cartridges in. I dont use the skimmer part at all mainly because its too loud and puts too many bubbles in the tank. I have a 30 gallon and the skimmer did produce foam when I used it, not a whole lot but I guess some is better than none. The noise is downright annoying! and so are the amount of bubbles. used as a filter only it doesn't make noise or put bubbles in the tank.