Eshopps Mariner 70 - Loud Sump noises

[Alatusvir]

Hey everyone
Recently moved and got a new Mariner 70 as my first jump from the AIO life. I got it set up and filled with water today and it is veey noisy. Im hoping someone can help me figure out what im doing wrong.

In the video attached you can hear water going through the drain pipe and also making noise when it enters the sump. The pipes are under the water but still sorta gurgling.

In the picture attched you can see the overflow setup.

I have a Jebao DCW-3500 for the return pump and regardless of what speed I have it makes noise still.

 

[Quietman]

Deleted - I was completely confused here. Apologies.

 

[CUSO4]

The instructions say that the elbow where the water drops into the sump must be underwater to stop air being dragged into the sump,
You need to iccrease the water level in the overflow chamber. I fitted a gate valve to the main overflow pipe to allow adjustment.