A biofilter isn’t a filter in the sense most people picture, it’s a habitat. It’s the part of a pond’s filtration system where beneficial bacteria live and break down fish waste, and its job has nothing to do with catching debris.
How It Actually Works
Media like foam, bio-balls, or lava rock exist purely to give bacteria surface area to colonize. Water flow carries ammonia-laden water past them; the bacteria convert it into less harmful compounds as it passes.
One Maintenance Rule That Matters More Than the Rest
Never rinse biofilter media in tap water. Chlorine kills the bacteria colony you’re trying to protect. Use pond water or dechlorinated water instead.
