Also try to get one that have a stable skimmer chamber that stays the same height regardless. Mine has a fuge chamber which is nice as I can use it but it doesn't stay constant height in the return chamber which is the only place I can put the skimmer. Unless I yank all the sand out of the fuge side and put skimmer there. But then I would have to basket the chaetos with in so it doesn't get sucked up.