Swirl Filter
From Ice Age Farmer Wiki
Swirl filters help to filter out solids (fish waste, etc.) from water, ideally before passing water into grow zones to keep from clogging any aspects of the system (pipes/valves/roots/etc).
Design
A most basic design involves drilling an appropriate hole for a 3/4" pvc bulkhead, about 75% up the way of a cheap 5-gallon bucket. Optionally, a second bulkhead can be added toward the bottom with an exterior value to allow for easy draining off of solids:
