I have a fish-only 5 tank grow out system with a 10 gallon sump. ONLY 90 gallons with 7-800 clownfish juveniles--no skimmer.
I feed heavily three times a day.
I do a lot of mechanical (siphon tank bottoms and change 100 um filter once or twice a day) and chemical filtering (PURA pad, change every 2 weeks), bioball biofilter, and water changes (20% or more per week). I do run a 40 watt UV.
My water is clean and clear, and the fish are healthy and thriving!