I added 2 female convicts...

[alleykat0498]

...to my 110 high which has 6 tiger barbs, (soon to be feeders) 2 O's (whom are finding that the barbs fit in there mouth) and 3 tin foil barbs. I have been so wrapped up in the purchase of my new arowana that I havent neglected that tank just havent paid as much attention. today I realized that the O's have splits in their tails and dorsals, and the smaller one is missing a nice chunk out of his pectoral fin. The barbs are notorious nippers and I was wondering if this was the barbs or maybe the two small convicts I added recently. I have watched the tank for about an hour now, at first I thought maybe it was fungal, but it seems to be spread out farely well on the fish that are affected. The convicts also have some fin damage, So is it possible that the con's attacked the much larger O's? Thanks guys. The parameters are all within acceptable ranges as well...

 

[Lupin]

Do the fins have white edges? Do tiger barbs also have a similar problem as the oscars and convicts? If the tiger barbs have no fin problems and no white edges on the fins are found either, I'd suspect the barbs nip them. You need to sort your stocks anyway.

White edges on tattered fins is a sign of finrot and deteriorating water quality. Do small partial water changes for now and increase it by 5% volume every 2 days. Water changes must be done daily as it is the only way to stop possible finrot from happening. Keep temperature steady at 76 degrees Fahrenheit. Any higher than that can cause the bacterial infection to develop quickly.

Your case is not fungal. True fungal infections are hard to come by. Usually, these cases are columnaris or bacterial infection mistaken for fungus.