You should do CO2 if you also want to grow the neatest plants fast and bushy or play with more interesting ideas. Since you don't have to care about fish, DIY CO2 should be easy in theory with big containers but if you can I think you'll love pressurized because after adjustment time you hide the setup and stop caring unless your plants show you should. And you can crank it and see what happens
If you want something a little lower maintenance and don't want CO2 but more of a long term garden, you should consider a Diana Walstad Natural Tank (I think this person's -- Betty Harris/thegab.org -- tanks are super neat:
Goldfish and Aquarium Board Article-Setting up a Walstad Natural Planted Tank ). If you're interested in plants, Walstad's Ecology of The Planted Aquarium will be interesting to you.
Either way (with or without CO2), you should also think about substrate, and again the Natural Tank folks will be very helpful and is great reading and we can apply these principles to any planted tank, and so there are folks using mineralized soil and great mixes that seem much lower maintenance and way smarter than, say, my Aquasoil as well. (I hope Ingg posts... but regardless check out his tanks in the Aquascaping forum.) You should think about Laterite and peat. You should absolutely get a good bunch of mulm and filter junk as the first layer for whatever substrate you use.
Can you do direct sunlight? I'm wondering if you'll need a heater inside but even if its on an enclosed entry or something inside but not heated a heater at say 72 should not be too bad for cost. UV may be necessary for GW, but they're cheaper than lights...
Theres lots of prolific and hardy snails you may want to consider too. Ruby red ramshorns are neat. Apparently there are blue ones and stuff now too. Pond snails/MTS/hitchiker snails are neat to watch regardless.
Super curious: What are you thinking of doing with it? Why no fish?
