[aquaverde]

XP1 if noise is not an issue.

Otherwise, probably Eheim classic series, not sure of the model, think the smallest is 2215?

 

[aquaverde]

Canister would be nice if you're injecting CO2, though. The HOBs always outgas about half what you put in, without some modification of the return or really strict monitoring of the water level to minimize turbulence.

They don't require much maintenance, either.