With 65W on a 20g is too high light with no CO2, IMO. You could look at a Coralife 30" 36W T5NO, which would put you at low-light. Big Als sells them, and I think they're cheaper than a 65W CF. If you do decide on CO2, I would suggest you invest in a canister filter, just so you don't out gas the dissolved CO2.
Otherwise, it's looking good...just make sure those rocks aren't limestone and good luck!