Gurgling from overflow

Hey guys, I searched for about a week to find a solution but I am still kind of confused. I have a really annoying gurgling sound coming from my overflow. It's not a flushing sound or anything and it sounds like there is no siphon (which there isn't) because it's basically flowing into a durso with no 90 elbow.

I have an in tank overflow which is not big enough to fit a durso. The plumbing is 1-1/2" in the overflow and I cannot fit the 90 degree elbow on the end of the tee. I even tried sawing a tee off and glueing it to a 90 elbow that i cut to shorten.

The tank is running so it's going to be difficult to remove the whole standpipe to fix this.

I had a thought which is to ditch the tee and just put 2 90 elbows together to get the u-shape for a durso and just do a reverse durso in the sump. (See attached really crappy paint drawing lol).

Am I over thinking it?

 

Bump..

 

Try putting a piece of airline down it.

 

Just run the airline into the water and then out the top of my overflow?

 

FYI, i built a hoffman gurgle buster instead and it is whisper quiet. Much easier to calibrate too.

Now I just need to silence my skimmer pump and LED fans.