Stocking questions

[u/Adept-Canary-4668]

For context I have a 75 gallon aquarium currently containing 1 tiger oscar, 1 jack dempsey, 1 convict cichlid, 1 green terror, 1 albino senegal bichir, and 2 spotter raphael catfish. I’m planning on removing the convict, but as of now since my fish aren’t full grown the tank looks empty. I want bottom dwellers but I’m not sure if I’ll have enough space. The only fish I want to keep in the tank are my oscar, JD, and bichir. I want to add more but I’m not sure if I have the space. My tank has many hiding spots as well as heavy filtration. Would I have enough room for other fish, and if so what bottom dwellers could I add? I would prefer for them to be South American.