I just ordered this light for my 25gal. http/www.hellolights.com/242xcoluaqho.html Do I need a glass lid over my tank then the light, or can I just mount the light over the water? This is all new to me, I've been a freshwater guy for many years. Is that light going to be good enough for some corals? My tank is 24" wide x 20" tall x 12" deep.