Noisy Overflow

[Carz]

I set up my 250 and the overflow is noisy. Its the bean animal set up. I have the water level set with the secondary overflow but it is noisy and not dead silent. I have a air hole drilled at the top of the secondary. If I adjust the drain valve it never quiets down. I have adjusted the flow until the water level rises and hits the overflow. Any suggestions?

 

[ndrwater]

Time.. unfortunately... I have a rural with a Maggie muffler (long story) on one of my tanks.. loud as all getout. For about a week.. then silent..