Well I did definitely see a relationship between BGA and light. Having my lights off for 2 days (not covering the tank) did make the BGA "ball up". I was able to vacuum it up today when I did a water change. Tank looks free of BGA at the moment. We'll see in a few days. BTW...I have 2 Tritons and 1 Phillips Colortone (30 Watts, 6 months) on my 45 gallon tank. Lights are on a timer for 10 hours a day. Sue