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The micron filter bags attached to the manifold that forms the lower part of the drain pipe. It attaches to the upper part of the drain pipe via a 2″ union coupling (on the left).

The micron filter bags in my setup provide the bulk of all mechanical and biological filtration. I am using six 16″ 25μ micron filter bags with draw tie from Customaquatics (Part Number: FI-ATPE25P1R). Each of my 2″ drainpipes branches off into three endings with female slip connections. These become a bit wider at the end, so that the filter bags don’t slip off when they are secured to the narrower part of the hose using the draw tie. This is the budget way to hook them up and obviously not quite tight, so that some water will slip through near the pipe and not be filtered by the bag. Customaquatics also sells special micron bag adapters‘ which presumable provide a better connection, but are expensive and I haven’t tried them yet. I will make sure to report here if I ever do.

The bags are very sturdy and can be reused multiple times. After 2 years of active duty, mine show no appreciable signs of wear. The draw strings are very long and very solid, allowing it for the bag to be pulled very tight around the pipe. Due to the air collecting in it, the first of the three bags in each sump sometimes floats to a large part above the water like a balloon.

This view into the sump shows all three micron filter bags fully submerged. The manifold is on the very right. On the left is a colander with crushed coral that had a titanium heater lying on top.