CO2 Distribution In Long Tank

[Ogpulchra]

I would like to inject a small amount of CO2 into a 33g long (approx. 48"x12.5"x13"), but I'm worried about getting enough circulation to distribute it throughout the tank. I am restricted to using sponge filters and most of the stock will be tiny nano fish that don't appreciate a lot of flow. I wouldn't be worried if it wasn't such a long, shallow tank. 

I'll have 2 medium Aquarium Co-op sponge filters at both ends and plan on having a pretty dense stem plant jungle. I considered adding a power head next to the diffuser once the stem plants really fill in. I could also add a manifold and have a diffuser at both ends. 

Am I worrying about nothing? Any input or advice would be appreciated. 

 

[nabokovfan87]

Trying to get a spraybar in there would be optimal.  Some sort of pumphead might be necessary. 

[OakenGoby]

This might be an option for you. You would need an external filter of some sort. Even a small canister would work. 

http://www.aquario.co.kr/unit/neoMixer.php

[Ogpulchra]

I am limited to sponge filters unfortunately. That's the issue. I'll probably just find other tanks to use the regulator on.