All my T5 bubs(tubes) are HO, so I am not sure whether your tubes will produce the heat that mine do (I also have 4'x6 tube fixtures). Just be sure not to get your tubes within 6-8" of your plants until you know what the heat produced will be. Standard T12 and T8 fixtures product little heat and you can position those tubes within 2-3" of the plants without worry.
