Need help with in tank sump system

[THE FAMILY GUY]

So I picked up a Free (fb marketplace) Red Sea Max 250 all in one aquarium. Very nice but this is my first time dealing with any type of sump system. The sump is built behind a glass "wall" at the back of the tank with a center overflow and 2 outputs. The problem I'm having is when I do a water change I turn off both pumps and proceed with my water change. After filling the tank up, one of the pumps starts making a slurping sloshing noise and there's little to no water in that chamber the other one is fine. I add water to that particular chamber but within 10 minutes the noise returns. Am I supposed to keep the pump on as I do a water change or am I doing something else wrong. Other than that everything is great.

 

[dmyersWv]

You can keep them on as long as they stay submerged.

 

[DN328]

So I picked up a Free (fb marketplace) Red Sea Max 250 all in one aquarium. Very nice but this is my first time dealing with any type of sump system. The sump is built behind a glass "wall" at the back of the tank with a center overflow and 2 outputs. The problem I'm having is when I do a water change I turn off both pumps and proceed with my water change. After filling the tank up, one of the pumps starts making a slurping sloshing noise and there's little to no water in that chamber the other one is fine. I add water to that particular chamber but within 10 minutes the noise returns. Am I supposed to keep the pump on as I do a water change or am I doing something else wrong. Other than that everything is great.

Not sure if you resolved this? If I'm understanding you correctly it sounds like water isn't overflowing to the chamber equally to the return pump. You want to make sure you have filled with enough water. Also, I would not leave on while doing a water change.