What do you want to know about them? I think it would take a huge tank to justify one, the main problem that I see is build up of junk in the filter, requiring a backwash every couple of days, and also the replacement of all the DE. If your only talking about using it for a couple of days a month to clear the water than I say go ahead, but youll need a pump powerful enough to use it. And use fresh DE each time, and be sure it flush it out really well after each use or the DE cakes up on the screens inside and kills the efficiency.