hi bro, thanks for the tip. My only concern is that the product claims to deplete oxygen. So by using it when lights are off may reduce oxygen level further, wouldn't it? I thought it may be better to use it when lights are on and when oxygen saturation level is highest. Also, by turning off the return pump, it may cut another source if oxygenation in the tank. Mine never came to the point if bleaching though when used previously in other tanks. Hmmm.. What are your thoughts? Worth discussing though to learn the best way of using this wonderful product. Thanks for sharing your tips though!