I have had the same prob. I was at first just runnin some NO lights. All was good. Then moved to VHO, got some algea. Put in 2 250 watt MH, and Holy cow did that stuff start to grow. I used tap water, and was like you, hunting for a crew to clean it up. But i have surrended to buying a RO/DI unit, and now it is starting to recead. Man, get ya a RO/DI unit. It will be a problem once you kick off that MH. I got mine around the bay that begans with "e". Or airwaterandice dot com i think, has some good deals. Have to check on that second one for ya.