Pond Filter Replacement Sponge UK | Biological Filter Media | Fits Most Pond Filters
Pond filter replacement sponges provide essential biological and mechanical filtration, removing harmful ammonia, nitrites, and suspended particles from pond water. Compatible with most pressurised and box pond filters. Available in two sizes for ponds up to 5,000 and 12,000 litres. Easy to clean and long lasting.
Why Your Pond Filter Sponge Matters
The biological filter sponge is arguably the most critical component in your pond's ecosystem. Beneficial nitrifying bacteria colonise the open-cell foam structure, processing toxic ammonia into nitrites, then into nitrates. Without a healthy, well-maintained filter sponge, ammonia levels can spike rapidly — particularly in warmer months — causing fish stress, disease, and potentially fatal consequences.
Key Features
✅ Open-cell foam structure — maximises surface area for beneficial bacteria
✅ Dual mechanical and biological filtration
✅ Compatible with most pressurised pond filters and box filters
✅ Can be trimmed to exact size with scissors
✅ Reusable — rinse and reinstall, or replace when worn
✅ Fish safe — no chemical treatment or additives
✅ Two sizes: small (up to 5,000 L) and large (up to 12,000 L)
Specifications
Specification
Small
Large
Suitable For
Filters for ponds up to 5,000 L
Filters for ponds up to 12,000 L
Foam Type
Open-cell polyurethane foam
Open-cell polyurethane foam
Colour
Black or Dark Grey
Black or Dark Grey
Can Be Trimmed?
Yes — scissors or knife
Yes — scissors or knife
Fish Safe
Yes
Yes
Delivery
Free UK delivery
How to Clean Your Filter Sponge (Without Killing Bacteria)
Never rinse filter sponges under tap water. Chlorine and chloramine kill the beneficial bacteria living in the sponge, effectively resetting your filter's biological cycle and causing a dangerous ammonia spike. Instead, squeeze the sponge in a bucket of water taken directly from the pond until the water runs relatively clear. Reinstall immediately.
Frequently Asked Questions
How do I know when to replace rather than clean the sponge?
If the foam has visibly deteriorated — crumbling, tearing, or permanently compacted despite cleaning — it's time to replace it. A healthy sponge springs back to its original shape when squeezed. Most last 2–4 years with regular cleaning.
Will it fit my filter?
The sponges can be trimmed with scissors or a sharp knife to fit virtually any filter chamber. Measure your filter's chamber before ordering.
Can I use it in a box gravity-fed filter?
Yes. The sponge is suitable for both pressurised filters and open-top box gravity-fed filters. Cut to fit as required.
Should I cycle a new sponge before using it?
A new sponge takes 4–6 weeks to fully colonise with beneficial bacteria. Adding a liquid biological filter starter when installing speeds this process significantly.
Should I replace all sponges at once?
No — replace sponges one at a time to preserve as much of the existing bacterial colony as possible.
🚚 Free UK Delivery | 🐟 Fish Safe | ✅ UK Pond Expert Approved
