I used stand-offs for my ballasts. I mounted then imside the stand and stood them off about 1-1/2 inches for the air to circulate around them.
125 Gal-35 Gal Wet/Dry-Tetra-Tec PF500 HOB
(3) AuquaClear 301 Powerheads-600 GPH
Automatic Tempature Controller
5-6 Inch Sand Bed-200+ lbs of LR