I have a Jack about 3 inches and a albino tiger oscar about 4-5 inches. Got them 2-3 weeks ago. I also have an albino chocolate pleco about 6-7 inches and a albino cory catfish about 2.5-3 inches (max size) but it is VERY FAT. I had the pleco and catfish for about 6 months now considering I got them the very first time I got the tank. Never had any other fish with them until I got my oscar and Jack 2-3 weeks ago. Felt like getting something new instead of having 2 fishes forever. The Jack and oscar really get along very very well. Never been any fighting. The problem is that I'm afraid that when the oscar and Jack gets bigger, that they would fight each other. I know oscars grow quicker thank Jacks. Will the oscar or Jack bully each other in the future when they get bigger or would they still live well with each other? And if you were thinking, NO the oscar or Jack doesn't try to eat the catfish. It seems the catfish is WAY TOO FAT for it to fit in their mouths . I do know it might try to eat it when it gets bigger, but I plan on getting a bigger tank from my 75 g, preferably 100 g or 125 g. NO BIGGER since I would be lazy to clean it every week .

I have a JD and 2 adult O's together and they do wonderfully!

They should be just fine, just keep in mind that all fish are different, so if you run into a problem, then you will need to separate.

But enjoy them! They are great fish, and good luck on the new upgrade!

I have a 8" JD and a 11" JD with my 2 7" red O's and besides from a bite from time to time its fine. When I first put the 11" JD in he beat the shit out of the O's but they soon learned to just stay out of his way.