Loud Overflow

[pterfloth]

Is the level in the overflow cycling up and down? If it is, the air hole may be too small. Mine plugged with salt a while ago and it was cycling and gurgling again. When I cleared the air hole, the gurgling disappeared.

I have installed a 90 facing downwards in my similarly sized overflow, fully submerged and the overflow is completely silent. Sounds like we have a similar setup.

Good luck, my tank is in my bedroom and has to be quiet.