What's your live stock? I feel it's difficult to say if a skimmer is needed or not based on the fact that it's a 55 FOWLR. Protein skimmers remove a lot of nasty stuff in a tank, due to a heavy bioload. I'm a firm believer in protein skimmers and feel they are an essential part of keeping a healthy salt water tank, and have been running one in my 55 FOWLR since it cycled. They will remove a lot of stuff a HOB filter cannot.