It works. My bio load is huge. I feed my sharks/eels 5 sardines about 9" long every 2-3 days. I also feed whole octopus, squid and other fish. Ive had about 5-10ppm with out doing anything to the aquarium for 1 year. I finally did a water change, clean the rocks and stirred the sand. I have yet to check the new levels. Ive used about half the sulphur that came with the unit. It was frustrating getting it to work but now its eaay. Hardest part is priming the pump. Im happy with it.