Forgive me for asking so many questions, but.... !
The sump didn't have any kind of Bio-media tower.

The plan for my sump is on a Word document attached (had to Zip it first to get it to upload). As you can see, water flows into area #1. If I seal it off and pass the water through a tank connector would this be sufficient?

I assume that I'm looking to keep the gas contained so that it can still re-mix with the water? However, I don't think it's just CO2. The drain seems to pull atmospheric gas down with it as well. Does this tend to build up in the chamber? If so, how I dispose it?