I've just set up a 75 gallon with a 30 gallon sump with a BM100 sitting in 10 inches of water. Total water is probably around 80 gallons or so. I have no fish in the aquarium and about 10 lbs of live rock. I've already emptied the skimmer three times. Granted it was not black but medium dark green with some solids. I'd say that's pretty good for little to no bioload. I have 2 hermits and I've fed a quarter frozen cube of food three times.