Ok, I have been doing this many years without much help. Not always the best result. Recently I have discovered the internet and the many books that are now on their way to my door. A friend of mine is also into having fish and bought a used tank from someone. My question is this, she bought a tank that the guy had a black light for use as a moon light. I have found nothing except that this may be harmful to the eyes of the fish. What's the story on this? He told her that it promoted better growth of algae (not always a good thing). Can anyone help?