The reason I ask, is I was mistaken in believing that the bio-balls were all the bacteria I needed. From "The Pond Guy's blog: Q: Should I clean my filter media or replace it?
Cindy – Dover, DE
A: Those plastic pads, BioBalls™ and Bacti-Twist® that live in your waterfall box, skimmer box and filter unit play a very important role in your water feature. The filter media’s surface is home to millions of beneficial bacteria, which are the biological filtration system in your pond.
Here’s a quick guide that outlines how to care for your filter media – and those tiny microbes.
Clean Infrequently: Once or twice a year, or when your water flow is significantly reduced, inspect and clean your filter media. Rather than scrubbing it spotless with soap or harsh abrasives, gently spray it down with your garden hose, being careful to maintain as much of the beneficial bacteria as possible while blasting away the gunk.
Replace As Needed: If the filter media looks worn on the edges or has gaping holes in it, replace it with some new media, like Matala® Filter Media Pads for extended life and performance, or with our standard reusable 2-inch filter pads, which are perfect for waterfall filters and skimmer boxes.
Seed Some Bacteria: If you need to replace your media, you’ll need to inoculate it with beneficial bacteria. First, test your pond’s water temperature. If the water temperature is 40-50° F, add Pond Logic® Seasonal Defense® to the pond or dump it right on top of the media in your waterfall box. If it’s more than 50° F, seed the filter media with PL Gel and let it set for one to two hours before putting it in your filter unit.