Euro reef, asm, and there are some new bubble units entering the market currently. others will recommend additional units they have had luck with. also if you want a sump and skimmer combo look into the CPR 194 or 294 units. I am curently using the CPR 294 and a Euro reef 250 RC. Others will post with additional suggestions. My recommendation is to at least buy one that is rated for your size of system at the bottom line and is rated for larger systems so if you have a 90 gal, get a skimmer that is rated for a 90+ system, not a 60 - 100 gal system. good luck.