help me silence the overflow!

[smokinreefer]

hey guys,

i've been trying to "neaten" up my old 180 that i set up budget ghetto style way back in the day.

so my overflow is pretty noisy and i figured i'd picked all your brains for some guidance as to how to silence this thing once and for all.

i'll attach a picture, so you can see the current overflow plumbing, please excuse the picture quality as it was taken with my phone.

the tank is drilled in the back and an external "durso" is in place.
the water level in the overflow is just above the 90elbow.
the drain runs down, then across to the other side of the sump.
a mag12 is used as the return pump.

thanks!