What is this awful gurgling noise

[sixline]

Tank is a Red Sea Max s400. Stock skimmer and overflow. I always keep the overflow adjusted so the water runs down the main pipe not the emergency backup. I also keep the water level high enough to keep from sucking any air into the pipe.

About 50% of the time there is the noise that you hear in the video. Unfortunately, there is a lot of background noise in the video so it is hard to heard the exact nature of the gurgling noise, but I was hoping it was enough to help someone assist me in identifying it and how to resolve it. In real life it is louder than it seems on the video, and it is such an irregular noise it is very noticeable and annoying.

 

[Ippyroy]

Sorry, not able to help. I have a similar issue, and it is because I did a poor job of designing the return plumbing. My overflow was noisy too until I raised the water level up to trickle into the e drain.

 

[splitting_lanes]

Try closing the drain valve a tiny bit.

 

[jeffchapok]

Mine did that whenever a whirlpool would form and suck air into the drain. I made some baffles from PVC and a drinking straw, then wrapped it in foam to silence it.

 

[Kris 2020]

I keep a trickle going down my e-drain as well.

 

[Neuratox]

I struggled with this problem too and wasn't able to find a solution online that fit my situation. My noise was coming from an air vortex that was forming as the water went down the primary drain. I built a triangle out of egg crate and hung it over the edge of the drain with the point of the triangle disrupting the vortex. I've got an image and better description here. Its been over a week and I haven't heard a peep - completely silent now.