i have a red sea purple and a powder blue in my 180.
they get along fine.
only had ick upon the first week or so of introduction for the purple...
and maybe a slight case of ick for the first couple of days for the powder blue.
my experience doesnt seem to be the norm though. most people seem to have more problems, especially with the powder blues.
hope that helps.
heres a pic of the tangs, probably within the first hour of introducing the powder blue. note, the white marks aren't actually on the fish, it's salt residue on the glass!
