Aquarium filters and filter media
Filtration is the part of fishkeeping that runs quietly in the background but does most of the actual work — clearing debris, breaking down waste and keeping water parameters stable. Getting the right filter, and replacing its media on time, matters more to your fish's health than almost anything else in the tank.
What's in this part of the shop
We stock internal filters, including the Marina I25 and the compact Fluval Mini, along with the filter media that keeps them working: foam pads sized for specific Fluval units, synthetic filter wool for mechanical filtration, and activated carbon for polishing water and pulling out odours and discolouration.
Mechanical media like foam and wool physically traps debris, while activated carbon works chemically, absorbing dissolved impurities that a foam pad can't catch. Most set-ups use a combination rather than relying on just one type.
How to choose
Match a filter to your tank's actual volume rather than rounding down — an undersized filter struggles to keep up, especially in a tank with a decent fish load. If you already have a filter, check the model before buying replacement media, since foam pads in particular are sized to fit specific units rather than being universal.
Filter media doesn't last forever — foam and carbon both lose effectiveness over time and need replacing on a regular cycle, generally every few weeks, rather than being left in indefinitely. A filter that looks fine on the outside can still be doing a much worse job than a fresh one.
In this section
Everything below is in stock with us, priced with delivery worked out, and packed and posted by hand in the UK.
Supa Synthetic Filter Wool
25g of synthetic filter wool for aquarium and pond filters, traps fine particles
£3.29
Supa Activated Filter Carbon
Activated carbon filter media for freshwater, marine and pond filtration systems
£5.45
Supa Filter Carbon
150g of activated carbon for aquarium and pond filters, replace every four weeks
£3.35
Marina I25 Internal Filter
A compact internal filter for goldfish or tropical tanks up to 25 litres
£25.29
Fluval U3 Filter Foam Pad
Fluval U3 foam pads that catch large debris as the filter's first mechanical stage
£7.89
Fluval U1 Filter Foam Pad
A foam filter pad made specifically to fit the Fluval U1 underwater filter
£6.09
King British Filter Aid+ (formerly Safe Water)
A live-bacteria water treatment for tropical, coldwater and marine aquariums
£5.41
Supa Condensation Tray
A 48-inch aquarium condensation tray, shielding the hood's electrics from tank water
£11.49
Aquatic Roman Gravel Jet Black
2kg jet black aquarium gravel, inert and colourfast for coldwater, tropical or marine tanks
£3.99
Pettex Aquatic Roman Gravel Natural Lakeland
Natural Lakeland-tone aquarium gravel for coldwater, tropical or saltwater tanks
From£3.99
Common questions
- How often should I change aquarium filter media?
- It varies by product and tank load, but as a general rule, mechanical media like foam or wool needs rinsing or replacing every few weeks, and activated carbon stops working once it's saturated, typically within a similar window. Check the guidance for your specific filter and media rather than leaving it indefinitely.
- Do I need activated carbon as well as a foam filter?
- Not always — foam and wool handle the mechanical side of filtration, while carbon adds chemical filtration for odours and discolouration. Many tanks run fine on mechanical filtration alone, but carbon is a useful addition if you notice cloudy or tinted water.
- Can I clean filter media instead of replacing it?
- Foam and wool can often be rinsed in old tank water and reused for a while, but they'll eventually need replacing as they break down. Activated carbon can't be recharged once it's saturated and needs replacing rather than cleaning.
Related
Written by Matt Garnett, who runs Giddy Pets and is a lifelong pet owner — not a vet. This is general information, not veterinary advice, and it cannot replace an examination by the vet who knows your animal. How we write these guides.