I'm going with a t5 because it will be about 17" off the ground in the enclosure so about 14" of the top of the substrate, I'm building which is more then the t8 is rated for. I'm one of those no heat device without a thermostat people. So will use one for my own peace. But thank you all for your advice. I've still got a bit of learning to do. Keep it coming at me I love constructive criticism.
The enclosure will be 48"X24"X17.5". Was planning to use an RHP for heat source.