Ok i have a 92 gallon tank with 1 tiger oscar and 1 pleco and im going to get 1 cichlid?

Question

will a jack dempsey be good in there with him and will i have to get a jack dempsey the same size as the oscar?

Answer 1

No more fish. 90ish gallons is the minimum size/territory for a single Oscar. With a Jack Dempsey you're going to have a big clash of personalities, especially with the Oscar having established territory, and someone's going to get badly hurt.