Overflow Matching To Return Pump Problem

[King]

ok i decided i had too small of a filtration system on one of my tanks, the pump was getting kinda sketchy too so i decided to just save the pump for water changes and move my overflow to a new tank i am starting up, the old set up was 500gph, i bought a 500gph pump, plumbed it, put that overflow on and started everything up and the return pump is putting out more water than the overflow is able to spit out. i also have a small thin bubble of air in the overflow tube from the inside to outside of the overflow that i cannot get out, i have been sucking saltwater for 10min trying. what can i do to get this straightened out? i need this tank to be running asap. the pump has no adjustment on it or i would just trying dialing it down a little for the time being. this is an older overflow i am assuming, it has a wide flat "pipe" from the inside to the outside and it has 2 outlets but only one flows water because the other inlet inside it is like an inch higher. like i said with the old pump this worked fine and has been set up for a long time. i get a new pump and move it all and its acting up. thanks in advance!

 

[King]

i set the level in my sump and my tank to the height i desire and within 30sec the tank is about to overflow. i am thinking about just ordering a new 500g over flow but i need this to run in the meantime

 

[@ombomb]

can you post a picture of your set up?

how big is the tank / sump?

 

[-Nemo-]

Picture would help.
If i'm understanding the situation correctly, if you plumb in a T-tube with a ballvalve on one side to turn down the pump, your problem will be solved.