I had Lactoria cornuta for a while. Most fascinating fish that I have ever had.
It was only 1,5" in length, but such fun to watch. I have a 12" Sohal and other big fishes, but the cow fish was fine with them.
Sadly I lost my Muu-Muu quite soon after it arrived. It got stuck on a Seriatopora hystrix with it's horns and had died. It didn't touch any corals, and didn't poison the tank after it's death. But as I said, it was really small...
He ate EVERYTHING right from the beginning: mysis, brine, flakes, pellets...
I'm getting a new fish soon, but this time I'm getting a bigger one...