Dovii get big, really big. 2'+ and they need very large tanks, about a 180 minimum for one fish. They are highly predatory and will eat any fish to fit in its mouth. If you want tankmates the tank will have to be much larger than a 180.
I have not kept dovii, but this is the general knowledge I have learned about the fish. Mojo has a breeding pair of dovii, and I bet he can help out a bit with more specific info.