I have four of them in my brackish tank, we did have one but its loud "singing" calling for a mate at night was driving us mad so we got three more in the hope that one would be the opisit sex and the noise would stop, which it has to a degree but on certain nights they all get going and its REALLY loud.
They can be difficult to feed and in a mixed tank so target feeding using a pair of tongs or a skewer to present the food directly in front of their mouths is recomended to ensure they are getting enough food. They are also fiercely predatory and will consume fish 3/4 of their own body length with relative ease, my largest one has eaten 3 puffers and 2 moray eels to date all of which i had thought perfectly large enough to be safe.