d2mini, I've had similar issues with my Geo Reactor and was able to get it working normally but you do have to tinker. This is what helped me,
First and foremost, purge all the air out. by turning your recirc pump off and increase your peristaltic pump speed while shaking Ca Rx. Next,
1. Check the connections to your circulation pump, mine had a leak
2. Set your psi to 4-5psi on your regulator. Just enough to get that bubble.
3. I have an aquarium plants regulator and set the bubble to 6-8 sec/bubble.
This worked for weeks until my ato stopped working and my peristaltic drew up air because the water line in my sump dropped. HTH.