That looks like a 125 tall. What's the foot print? If it's a 6'x18" footprint, you can have more sa/ca's than if it's a 125 tall.
Personally, I wouldn't keep a RD and flowerhorn in a 125 together... Maybe at the size they are now, but once they're both 14-16", they're going to want to kill other things in a 125.