My overflow drain has gas

[outtafocus]

Adding the 45 helped reduce some of the sloshing and burping, but because it is also adding more back pressure, I feel I am getting more fluctuation in the water in my overflow chamber. Bigger water rise, more pronounced flushing.

I have come to a conclusion that I may have been trying to force too much water through my overflow. When I added the new Rio 20HF pump is when I started to noticed the flushing. I used my ball valve to throttle down my pump and it seems to have reduced but not elliminated the flushing effect. My overflow plumbing has no problem handling the amount of water I am putting through it, but with more water comes more air being sucked in to the system.
I was looking to get away with no powerheads in the tank and relying on the return pump through a SCWD for my only circulation. I think I am going to return the pump and use powerheads for movement.
Now I just need to decide if the Mag7 I own will be sufficient. When I was doing my initial water tests with the Mag7,I had no flushing issues or sloshing. I believe even a Mag9.5 may be to much flow.
Big Als said I could return the pump if I didnt like it.