Sunp fuge containment

[Aluco]

This may seem like a simple question to some but my refugium section in sump has an opening leading to the return pump. My cheato keeps floating over into return chamber. What would be the best way to contain the algae in the refugium section?

 

[A_Blind_Reefer]

I’m having a brain fart on the name but cut to size filter sponge. Most aquarium supply places sell it. It comes with some sumps as a bubble trap. Make it a little taller than the divider to keep anything from floating over to the pump

edit. Some use plastic egg crate material. I found that chunks can make it past that though.