Trying to understand; the water from the tank flows into the first/left compartment, overflows the top of the first partition and then must go through the sock to eventually flow under the second partition and into the third/final compartment which contains the return pumps?
Where is the noise coming from? It seems as though the only source of noise in this sump is the point at which the water enters from the tank?
I'm not into filter socks at all, so perhaps I am misinterpreting what I think I see. To me, it seems that the discrepancy in water height between the two sections can only be caused by the clogging of the pores in the sock, and will only get worse as time passes and as the sock collects more debris. As that occurs, the height of the water in the front portion of the sump will increase, and in this sump it can only go up a very small amount before it begins to spill over the top of the second partition and bypass the sock altogether.
In a planted tank, and/or a heavily-stocked tank, this will happen quickly, necessitating very frequent cleaning of the sock; my mech filtration is sponge rather than a sock, and is set up so that the water level above the sponge can rise to a height of 6-8 inches, which "pressurizes" the water and forces it through the slowly-clogging first filter layer. If I experiment with not touching it to see how fast it clogs up, I find that a sheet of 30ppi foam will clog up to the point where that "head" of water cannot force itself through the sponge within a week or so. Layering the foam with coarser-to-finer levels extends this, and a layer of poly on top of the foam extends it even further, but I like to clean the top-most layer at least every couple days, and ideally daily, to maintain a free-flowing filter with no bypass of dirty water into the biomedia.
In your sump I see some sort of blue pad in the first compartment; is that a coarse prefilter to keep your sock cleaner for a longer period of time?
