Sixline wrasse, Shrimp gobies, firefish (they jump, though, so watch out), some of the cardinals, a great species tank for dottybacks, skunks or ocellaris clowns (tomato's, clarki's, and marroons can be aggressive if you want any other tankmates), some of the tiny basselets, little gobies like the twinspot, rainford's, etc, etc. :wink: HTH
The standard 55 is 4 ft. in length. I share the belief that a juvenile tang would be "okay" for a short time, but ultimately these fish need more horizontal swimming room (read 6 ft. tank). It may not seem like a huge difference but these fish are distance swimmers so longer is better. The 13 inch width of a 55 is also rather restrictive.
Ultimately being the key. I wouldn't dream of buying a mature adult tank and cramming him into restrictive confines of a little tank. Right now I myself have a Kole that is 3.5". In my 54 (36x18x20) I think he is quite happy. He is the fish in my system. When he gets a bit bigger then he will be given away to a person with a bigger system (he has a 230). I don't keep him to be inhumane or cruel, and if I could offer him my wifes 85g vivarium I would, but he was the algae eating fish I wanted and has been well rewarded.
any type of a tang is a big NO.
got with something like a 6line wrasse, coral beauty, royal gramma, chromis are cool too. Pygmy angle about any goby would work also.
I had my yellow tang in my 55 for about two years and he was fine. I now have a 125 and I'm not sure how well things would have gone if I kept him him there. I would caution you on adding a tang even though I did it myself. Maybe I'm being a hypocrite or maybe I learned my lesson, or maybe a little of both.
I have kept a yellow tang in a 55 gal (4 ft) for about 8 years without a problem. They do roam a lot in the wild, but their style of grazing and swimming makes it a lot less of a 'suffering', if any when compared to, say, a Naso.
add some bar gobies they do great. Add 2-3 will be good. If you have only one the it may stay hidden (it has that fear unless in numbers mentality)
ruski