pushing it, but the koles yellow eye, gets 6 to 7 inches, and although they should have 75 galons, they really in my opinion need a good 4 ft(55 is 4ft) and should be able to do ok(BUT NO SMALLER), in a 55
i really like to see tangs in larger tanks, so i am not reccomending it, but most will get one anyhow, in your case, if you are i would look into the koles(and do not look at the pics you find, THEY ARE NO GOOD, the fish is much more beautiful in person)
HTH