ok, I have an 18,000 gal ag doughboy with a powerline pump by doughboy and an aquaview filter. Are these good pump/filter? I had no idea there were so many out there - I just got whatever they delivered. Now, this morning when I got up, without checking this message board first, I went ahead and backwashed. It was clear in the bulb at first, then very sandy and it ran a good minute or so. It stayed sandy, but got a little better. I turned it back to filter and it seems to be working correctly now. I am still worried, though, that something is going to be wrong and I may be tearing up something. Oh, by the way, THANK YOU for helping!