I use rockwool. Try growing with all mediums. There is no best medium. (except organic soil)
(I see why you said that... because of the algae.) I use plastic covers on the top of my rockwool. If you do not you do get bad algae. The algae has never done any harm to me.


T5's would work good. Not as good as a HPS. The T'5s would really help with heat issues. The T5's would look good in your setup. LED's are nice but pricey. I would do some research before getting lights. I love my HPS. Most people do start out with T5's or cfl's.