imo the depth isnt too bad, but the width might be a problem for only one bulb. Just today I upgraded my light system to 3x 250's. I have a 48" 2x 150w's system I dont know what to do with. My pm service is turned on.
I think purge was talking about the 40" length. A single MH bulb will likely result in insufficient light at the ends of the tank. I have 3 for a 72" length, so its 24" for each MH bulb. Even your 96W CF won't reach a 20" depth, HO T5's will have a better chance.