I have a 180 litre tank which currently has 3 congo Tetras, 5 Phantom Tetras, 2 Rainbow Ram , 1 Swordtail , 4 Tiger Barbs, 1 Plec. The latest edition was the Tiger Barbs I bought 6 and two have died I don't know why the water is fine so I assume from stress of moving but My swordtail is very...