have a 55 gallon tank with 1 tiger oscar, 1 red pacu, 1 bala shark, 2 convict cichlids, 1 bumblebee cichlid, 1 synodontis catfish, 1 common pleco, and 1 green terror. all are juveniles, the bala shark being the largest at 5" long. is this overstocked? also, lately my oscar has gotten small frays that look like bites in his tail fin and the tips are white (about 2mm line on the tip) all the way across. is this finrot? what should i do? i feed them tropical flakes, oscar grow formula, and frozen foods (beefheart,brineshrimp,bloodworms). the tank has 1 small piece of driftwood, 1 ceramic large roots cave, 1 smaller sphinx cave and some plastic plants. gravel and river rock substrate. the filters are 2 penguin 350 biowheels. water changes every sunday, ive had them for 2 months.