you could grow some emerged aquarium plants. its super easy and grows much faster than underwater because you dont need Co2 injektion. you can find guides here on YT. then you always have plats for the tanks. and maybe sell some later.
just be aware that those oscars will need a much bigger tank! They get to 10-12 inches in length and will need to live permanently in a 75-90 gallon tank minimum. Otherwise they're awesome fish!
