ista max mix co2 reactor

[Ravi sood]

connected ista Max mix co2 reactor to outlet of ehiem 2217. after switching off the selenoid ista reactor shows air pockets on the surface of reactor for hours and takes approximately more than 5 hours to clear air pockets. . my question is are these co2 bubbles or air bubbles sucked by the inlet of canister from tank.

[BFG]

It might be accumulated co2 or even o2 .