We have had this tank for about 3 years and the same fish have lived in it. We added another tetra to the tank about 7 months ago and all the fish are doing fine. About 2 weeks ago, one of our neons looked to be pregnant....the only change was adding the additional fish. Of course we all think that the new fish bred with it. We bought a floating net tank/cage for it so if it did lay eggs they would be safe from the other fish....but if it is sick, I don't want it to get the others sick. We need some help!