VRWC;4780088; said:Get a bigger tank. A 40-50 gallon tank isnt big enough for a single one of those fish, let alone 3 if they are over 3 or so inches...that and research fish next time before you buy them. A single oscar, when larger, will need a minimum of a 75 g tank and really, the same goes for a JD, even though some people keep them in 55g tanks. Bigger is always better.
If getting a bigger tank isnt an option for you, get rid of them all and get some smaller growing cichlids like convicts, sajica, honduran red points, salvini etc.
I don't always agree with you on a lot of things. But this is one I have to, that's just ASKING for issues. Fish fighting in a cramped and tank that has poor maintenance is unfortunate for the fish. Injured fish don't stand a chance at healing and staying healthy. I have 5 tanks in my room that range from 5 gallons to 110 gallons. The 110 gets a 50% change once a week, the rest get 2 50% changes a week. Sure it's a lot of work, but I love my fish and they're going to get the best care possible to keep them healthy and around for a long, long time.