hangon? or sump? prizm imo is cheaply built but they don't cost alot. i would ge a remorapro for a 55g. Much bigger and better built. But if you have caulerpa in your refugium a prizm maybe fine. Just depends on how much you want to spend and what quality you want. IMO alway buy a skimmer rated at least double. If you have fish feed everyday you won't overskim.