first off let me say sorry for asking so many questions im sure its getting anoyying and also for not taking the time of day to proofread my posts...i kow that must also get extremly anoyying.but onto my current question.the light ive got coming in the mail i beleive was a 18watt light not sure wheat type but i remember its 18 watts and has some moon thing on it so i can change it and its blue it look really cool.it used to be my dads..ive also got my stock light that came with the tank that i know nothing about...with that 18watt will i be able to grow any corals in my 20g?or will i need to upgrade?if so what would be best?i beleive someone suggested a viper MH but ive been reading about them and apparantly they can get hot and are very expensive..i dont really want to buy a light and a cooler so im looking for somehting that doesent get too hot