oscars in the early 90's and late 80's were stronger than they are now. back then it was rare for an oscar to ger hith. . .even my aunty had hers and they were raised from 2'' to 14'' in just a 3foot tank with prehistoric 'air powered under gravel filtration' and none showed any health problems. . that leads me to think that the species has been over bred for the aquatic hobby and their genes have weakened, thats why its so common to hear oscars with hith these days.