Very cute ad nearly irresistable. But if you're planning to keep corals he's a HUGE mistake. He might be the very unusual exception to the rule, but cowfish eat corals, clams, crabs etc... they jump out of the tank pretty well, and if upset enough they will exude the above mentioned toxin and Kill Everyone in the tank, including himself. There's no way to clean up a cowfish toxin spill... but it is rare that they do this.
The worst part is LR
filtration isn't enough for these guys. Their waste is high in ammonia and they tend to produce a lot of waste for their size. frankly, cute as they may be they'e a headache as well.
I hope he works out for you.