75 gallons is pretty much flat out not big enough for the Hippo/Regal Tang aka "Dory". You can start with one of the tiny ones and keep it for two years maybe but then you are going to need to get it out. Anything under 160 gallons just wont be large enough to successfully house that fish long term. I think that's where the powder blue reccommendation came into discussion, because they max out at 9 or 10 inches, nowhere near the 15+ inches Regals attain. For a 75 I'd stick to fish that are under 10"
- Misti
"Take care of the water; the fish will take care of themselves."