Pond Filter Bio Balls

When topping up or replacing bio balls, it's worth checking that the quantity you add suits both the size of your filter chamber and the overall volume of your pond, as too little media will limit biological filtration while overpacking can restrict water flow through the unit. Bio balls work best alongside a mechanical media layer (such as sponge or foam) that catches larger debris before it reaches them, keeping the surface area free for beneficial bacteria to colonise. If you're unsure how much filtration capacity your setup actually needs, our Pond Filter Size Recommender can help you work it out. A quick rinse in pond water during routine maintenance, rather than a full clean, will help preserve the bacterial colony you've built up.