i'd go for an hob or canister rated for a size up, so 20 to 30g rating. as long as there is not too much current for the plants you want, i think any would be good
i have a peanut butter jar attached to a an aquaclear 20 powerhead. the jar is filled with fluval biomax, fluval pre filter rings, foam and carbon. the flow from the pump has been reduced by i guess 50%. works great and is alot of fun to run too.