Hi Shane,
I have a 50G (close to yours) and I'm using 2 x 39W T5HO tubes.
This brings us to about 1.5WPG. No overkill.
Fits in the tanks with low PAR value. (I think

)
Other than the occasional green spot algae on aquarium glass, I'm pretty much algae-free.
Hope it helps,
Regards,
Ryan
P.S. It'll be good if you already have a PAR meter so you can test out the T5 tubes in your tank. I'm trying to budget for one but I'm afraid the Reefcast offer might be gone then.
