hmm, why not take the glass cover off? If you're worried about your fish jumping, lower the water just a bit. Because he's got long fins, he can't exactly jump very high, and probably wouldn't waste his energy trying. Personally, I've never had an issue with jumping bettas.
Spending that much money on cartridges might not be a good idea. if you use the red sea nano, you can cycle (carefully) with your fish in then tank with plent of plants, once it is cycled you won't have to worry about carbon cartridges, seeing as the bacteria that does that work will be living in the sponge.