I have two right now. Lovely critters, but the males will drive a person nuts if kept in a bedroom at night (mine are about five feet from my bed!).
They are okay with SOME fish, though it is best if they are kept by themselves (just the five of them with no fish in the tank). They are easy targets for nipping, and will eat any fish that are small enough to be eaten. Fortunately, they're so small that the only things really small enough for them to eat are fry, so they can be a means of keeping down fry populations. If you see ANY nipping by your fish on the frogs, then they should be immediately separated into their own tank.
One major concern with keeping frogs in community tanks is the fact that they aren't too bright about eating. By the time the frogs realize there is food in the tank, the fish have usually already eaten it. To prevent this problem, feed the frogs live blackworms and frozen or live bloodworms SPECIFICALLY to them by use of a turkey baster or eyedropper. Do not expect them to eat flakes or pellets, even if they say that they are specifically made for frogs.
As for sexing...the males have a small light pink or white pimple on their sides underneath their arms. Females may also have it, but on males it is larger and more obvious. Also, females are wider and bulkier at adulthood, while males are more slender through the torso. Another thing is that females have a small stub of a tail, more than a male does.
