Help needed

[cclarky]

Hi all need some help please
Upgrade my tank to a Redsea 260 with a back sump plus a upgraded sump
The problem is I can’t get the flow right
2 x pumps in back sump
Redsea reefmat 500
Redsea 300 skimmer
Constant fluctuating in return chamber
Pump running dry
Adjust gate valve and pump flow and Still can’t get the flow I need
Getting to the point where I wish I didn’t upgraded
So please any help
Thanks

 

[MarineandReef Jaron]

I am very confused. Which pump is running dry? Is the water level in the back at the red line. This is where it should be.