Sounds like it's doing the right thing.

The tube on the side is to count the bubbles and to provide input for the CO2.

The hole on the opposite side from the powerhead is the burp hole, this releases excess gas if needed at night/adding too much for the reactor capacity.

The venturi loop, the tube connected to the powerhead, the the gas bubble will build up over the course of a day and then that part will kick in once it reaches further down and collect more gas. Then the gas will be sucked into the loop and produce a fine mist that's explled out the bottom.

Sounds like you are not adding enough CO2 gas to the unit, you should see mist at about 1/2 way through the light cycle.

Regards,
Tom Barr