[steri]

That really depends on whether or not the tank is a reef or a FOWLR. Most butterflies are bad in reefs. Most angels are hit and miss with reefs. Some work, some don't and there really is not much ryhme or reason to why.

You'd probably have the best luck with a different shaped tang (such as a blue hepatus) or a dwarf angel (such as a flame or coral beauty). Hope that helps.

One thing to watch for though. I have often heard it is best to add yellow tangs last in a tank because I have heard that they tend to be the most territorial of tangs. So whatever you get, assuming the yellow is already in your tank, just watch for him in case he gets aggressive with new fish. There are ways to combat this if it happens (such as putting a mirror up to the tank, or reaquascaping the tank), but just know that it may be an issue with new fish and a yellow tang.