This is based off of the designs by Paul_B on ReefCentral and others in this thread:
http://www.reefcentral.com/forums/showthread.php?t=2113800

The premise is that brine shrimp (baby or young ones) are placed inside this unit, then the unit is put in the tank for Mandarins, Seahorses and other slow feeders that can eat the shrimp though the net. The net keeps the shrimp from escaping in to the filters of the system.

This model is magnetically attached, so the user can fill it, deploy it on the side of the aquarium, and retrieve it.

Use some fine mesh (pantyhose) to cover the ring, then press the ring in to the lid. Apply some super glue if needed, and trim away the excess. Fine Tulle was still too large of a hole size (as pictured). I have some micro mesh on order to try, but pantyhose is reported to work well.

Use a 32mm x 2mm rare earth magnet. Cover the magnet holder lids with a thin film of aquarium sealant, then press in the magnets. Give it another coat and make sure to coat the edges of the lids. Press the lids/magnets in to the base and the external magnet holder, and clamp closed with a spring clamp or similar. Allow to dry for 24 hours.

I don't yet know how long the magnets will last, it depends on what you printed this in and how well you seal it. I've used spray-on Plastidip to coat magnets, but with only a few weeks of use I don't have any long term reliability information. If they fail, I'll update this site.