You could do 1 silver arowana, 5-6 peacock bass, 3-4 oscars, 3-4 rays and maybe a niger cat. This would be nice stocking level and would not require to much maintenance yet still could allow room for more fish
Yeah that sounds like a good tank,9' x 5' x 4' make 1300 gallons though, 9 x 5 x 3 makes 1000 gallons. Tile is better than substrate as it is easier to maintain. What is it going to be made out of