This question is not about an octo tank. After the death of my six month bimac I decided to test my ability to keep a reef tank. There seemss to be an abudence of advanced aquariests at this site so I thought I'd throw the question out. Now it may seem like a stupid question but what is the difference between metal hallide lights and hallogen lights. The self contained MH lights that have two sided bulbs look almost identical to the hallogen light that mounts on a stand. Would the hallogen lights work? Do they have the right light spectrum? Do they simply get too hot? It seems Im clueless in this area.