I have a eshopps overflow box on my 125. And it's just trickling. I had the tank set up before. It crashed while on vacation so I cleaned everything out and I can get the overflow flowing.
Why would adding a barbed return jet slow my return down to almost nothing. Took the return jet off and the tubing flowed fine. Ran water through the jet and it came out fine
Jets can be pretty restrictive in terms of flow. You are generally increasing the exit velocity at the expense of pressure drop and flow. If you do not have a high-head pump to overcome it, that could be an issue. I generally prefer to not put anything on the returns that restricts the flow and add powerheads to achieve the flow in the tank.
What return pump are you using and what is the jet model/size?