Hi all, I need some help. We have a 180L freshwater tank with the current fish - x3 angels, x1 plecostomus, x1 albino catfish, x2 cory catfish, x9 gouramis (x1 moonlight, x1 gold, x1 pearl, x1 red, x2 neon blue, x2 powder blue, x1 yellow) and a red tailed shark. I have recently noticed one of my angels has been attacked, its fins are looking rather diminished. But I haven't seen any other fish attacking it. Anyone know out of the fish we have who the likely culprit might be? All the fish are reasonably small as we only started the tank in October last year and got everything very small. I have seen the shark chase the other fish at times but that's it. Also we are thinking of adding some swordtails, would this be ok? Any help or advice would be appreciated.