I siphon as much as possible on a 25% water change . But i agree what you want to do. The uv would do the rest.Q. When I get the filter floss for the poor mans UV, Can I also use that to siphon the sand bed - turn off the ATO and pumps, siphon through the floss into a bucket and then return the filtered water into the tank? Or would that be counter productive by removing the good organisms I'm trying to cultivate to fight the dinos?