To control my Spg I built a auto top off. I use a float swith and a pump to pump rodi water in the aquarium when it evaps down. I also added a Tunze Kalk osmolator but that another conversation. It cost me like 50 bucks to build it. Works great and spc is always the same! By the way T-5's ho with parabolic reflectors would work great! MH may cause to much heat and then you would need a chiller. No fun!