Didn't realize these things are still around. I had one on a cichlid tank back in the 90's. Very healthy tank w/no ammonia or nitrite problems. Had some issues with nitrates, but that was to be expected.

I did replace 1/2 the sand every 6 months to help keep nitrates from accumulating. Never used one on a salt tank. Be careful with a stronger pump. When I first hooked it up, the pump was too big and blew out all the sand.