Sorry -- it's an idea Calfo suggested on reefcentral (just before he stopped posting there or whatever that fiasco was back in December/January) to reduce nitrates in a SW system without having an actual DSB in the tank (and all the problems associated with that -- ie. cleaning the sand -- in a remote unlit bucket, with enough flow-through, theoretically no detritus settles on the sand, thus keeping it clean blah blah blah). Like most other RC topics there's a 13-billion page thread over there if you have lots of time to read though lots of talking about it.
PS. Thanks for posting the link Christy
