I have a 29 with a diy sump with a 2.5 gallon section for a fuge. I was running a 50w led grow light on it which was putting out 600 par at the water surface. Tank is stocked with two clowns, royal gramma, clown goby, and a fire fish. I not changed the water in 8 months and I have to dose nitrate and phosphate. I mainly feed frozen food. I had removed my skimmer cup around thanksgiving because my nutrients were dropping again. I swapped out the led for an old small t5 fixture to try and reduce the amount the macro was growing. With a 20 display fuge you will need a lot of food going into that tank to keep any nutrients in the water. I got dinos twice because my nutrients bottomed out.