good question.
I have a 75 with approx 5 gallon wet/dry sump.
the wet dry sump has a huge media field for bio media and once the tank cycled the filter quickly adapted to any bio load I added..
this tank has 4 juvie discus, 3 growing angels, 3 keyholes , 2 bolivian rams, a bn and 3 oto's.
It is lightly planted(soon to have more plants in it) ph7.2, 0 ammonia, 0 nitrites, 20ppm nitrates.
I change 20-30 gallons in this tank 3x week.(fish are fed 3xday)
so far no problems. I am waiting to see what happens when the fish reach adult size.
the discus are growing fast and were moved in about 1-2 weeks ago after 3-4 weeks in quarantine.