I'm still dosing CO2 in my 75g. Both tanks will have injected CO2.
What I did was put the new cylinder and equipment to the 75g and hand down the older cylinder and equipment to the 29g. Once I saw how wonderful it was to have injected CO2, I couldn't NOT add it to my 29g. In a way, the 29g will be a smaller version of my 75g.
The lighting I have on my 20long in the picture above is one
dual bulb Coralife Aqualight FW 30" fixture. This fixture is about a year old with one 6700K T5 bulb and one 10,000K T5 bulb. Now they're using a "Colormax" bulb in place of the 10,000K bulb. Mine went out about a month ago, and I decided to replace it with the original 10,000K bulb. So that bulb is new with the 6700K being old.
I now have two of those fixtures (the second fixture has the Colormax bulb instead of the 10,000K bulb). That's what I'll use as my brighter lighting for the 29g. It won't be as bright as my 75g, but it should be bright enough to grow what I want.