Ideas? rubble or bio balls?
 

We are just setting this tank up in our store. I would like to put small bits of live rock & rubble in the second chamber instead of the bio-balls. Does anyone know how full it should be? I thought about 4-6" loose rubble would be good. Does this quiet the noise? Any other thoughts?

what kind of noise are you trying to quiet?

the sound of the water flow. It is better now that we put the top tray in the right way. oops