bought 3 gouramis on Sunday and 2 have died.........the third is looking healthy!!! hes eating, swimming around lively and doesn't look bothered with my mug looking in on him!!!!!!! could he have nibbled the poor other two to their sad demise? I say this because they both had split tails ? any ideas please? all tests result ok....ph nitrate nitrite the only one i havent tried is hardness.