I never had any problems with my seaclone, I had the big one, but I got a turbofloater on ebay and the seaclone is now gathering dust in the closet. My seaclone worked fine on my 55 and 75, but I ditched it when I upgraded to 100 gallon. I think it was rated for 100 gallons or more even, but I don't trust those ratings much.
I have heard good things about remora and bak-pak skimers for smaller tanks, but I like my turbofloater needle wheel skimmer. That thing cranks out tons of dry foam, but it is kinda tricky to set up.
Whatever you do, don't buy a skilter or a visi-jet. I have owned both and if you thought a sea-clone clogged up, you have not seen anything until you have owned a visi-jet. Skilters are just wisper hang on filters with noisy, crappy 6" tiny skimmers built in to them, and they suck.