A picture would sure help, but...

There is something wrong and I doubt your CO2 is going to mix properly with the water.

You need to make a way to bleed off the extra air. On my reactor, I drilled a hole and glue a small piece of rigid tubing into it, to which I attached a small piece of clear flexible tubing with a valve on the end (a simple stopper will do, but hard to get on and off). When my reactor has been drained for any reason, I open up the extra bleeder valve until the water comes up and shoots out of it. At that point, you can close it up and your reactor will stay filled with water until you change water or otherwise drain it.

You might also want to put a venturi loop in your reactor back to the pump. Tom Barr designed a very nice DIY external reactor (the one I used) and there is a good thread here in this Forum that explains how to make it. I especially like the way his input for the CO2 is designed compared with yours.
Dual venturi DIY External CO2 reactor

With minor modifications to the impeller, you can also feed the CO2 directly into your powerhead and avoid a reactor altogether.
Another method for CO2 diffusion: needle wheel powerheads