Ok I had the guy from the LFS come look at my filter, he thinks I have a bad O ring and is ordering me a new one. I thought that the filter canister would be running higher than atmospheric pressure and he thinks that the filter would be lower the AP. My argument is that the whole canister is pressurized by the pump building pressure to force the water out ( Hence why the pump has to be below the fish tank) and he thinks that since the XP4 is PULLING water through the filter media the whole system is negatively pressured and is pulling air in under the O-ring. What do you all think?
Oh and No I dont have any airstone at all, I do have a CO2 injector but it is not the cause, I tured it off foe a few days to make sure.