[Pescador]

It probably wouldn't be enough algae to do much for water quality anyway but you can make a zooplankton "reactor" with any dense inert material and there is no maintenance. Different media will encourage different organisms. Rock rubble is good for larger micro-crustaceans. Finer material for smaller organisms. Spun plastic fiber pads, algae scrubbing pads, foam prefilters, dacron, hung or stacked openly will promote amphipods, copepods, and mysid shrimp.