The hole @ top of durso looks like approx. 1/8 - 3/16 .
The water drop into overflow is approx. 1" .
On the bright side I found my missing cleaner wrasse in the overflow !

figures that where he went my clowns love it in there, for future reference if a fish goes mia check the overflows and the sump one of those inspection mirrors comes in really handy for that. is the outlet below operating level of the sump. does the level in the overflow fluctuate much i'm pulling straws now

durso
 

is your air vent adjustable on your durso or is it a hole drilled into the top.if it's just a hole ,try putting a mini ball valve on top to adjust the air

The vent on top of the durso is a nipple ! I could attach a piece of air line then control by pinching but I've been listening & reading & decided I'm happy with it !!! It's quiet but not silent . I think I'd switch to Herbies if I want it silent . So I can live with quiet right now & if it still bugs me later on I'll switch . Thanks for the input .
Mark

Scrap the stock overflow, do your return line over the back of the tank and install herbies

For sure go with herbie's if you want it totally silent! :smile:

you know your never going to get "Silent" with a overflow set up, some oare closer to silent than others, but none are totaly silent. it all depends on the other ambiant noise in the room. want your trickiling water to be silent then get a pump that makes a little more noise and you won't hear the trickle anymore :mrgreen:

the best noise reducing pipe I have found is flexable PVC, its softer, more flexable and thicker, so it deadens the noise more. can try using that and replacing the PVC piping with it. befor you replace regular piping though you can go to a hardware store and buy that foam pipe insulation and use that to see if it makes a difference.

Steve