I recently set up refugium in my sump with some of this green grass stuff (can't remember name) I got from B and B and also a few mangroves. I put my old pc light from my old deco 3 nano tank on it and I need to know how long to leave it on. Some say 24 hours a day and others have said to have it turn on when the display lights go out, what do I do?? Oh and maybe it's just me being crazy but it appears that my water clarity got way better with this new addition, has anyone else notices similar results or am I being crazy?