I have two going now (one in each of two 7 gallon nanos). What it produces in a tank that small has never been ‘thick’ skim material, but definitely green water. I figure that’s green water that my fish would otherwise have been swimming in (lol). It does help to replace the wood block (air stone) every now and then as it gets slimed-over with algae, and using a plastic thumb valve somewhere along the air line will give you better control— I can’t recall whether it comes with one automatically. Of course, for the price you could double-up and run two in one tank and crank them both up, if you needed to cope with a heavy bio-load. Best wishes.