my sun sun has a surface skimmer which works good.
The problem was when i added a sponge on the bottom, it reduced the flow going from the bottom, and made the surface skimmer pull more.
This also made it pull air when it was skimming, and well... i wasnt kidding about a max mix reactor having problems..
When this setup @ 2BPS isnt holding lime green on a small 10 gallon:
You know your losing a LOT OF CO2.
Anyhow.. i removed the surface skimmer and BAM, in 20 minutes i got my lime green again.