ShuRex Small Aquarium Filter Cartridge Refills, 12-Pack, Three-Layer Carbon Filtration

ShuRex Small Size Cartridge Refill is a replacement cartridge for compatible small fish tank filters, with three-layer filtration and a 4 × 2.2 in (10.16 × 5.59 cm) size.

• Designed for 3–10 gallon (11.4–37.9 L) small-tank filters — sized for the stated aquarium range.
• Three filtration layers — microfiber cotton captures solid debris while activated carbon absorbs odor and discoloration.
• Compatible with Tetra Small Filter Cartridges S Size and several named alternatives — helps you match the refill to your filter.
• Tool-free, hands-out-of-water replacement — designed for convenient installation.
• 12 refills, presented as a one-year supply — keeps replacement cartridges on hand.

Small aquarium filters need replacement media that fits their cartridge holder and addresses the debris and discoloration collected during filtration. ShuRex refills are made for small fish tank filter applications, including the stated 3–10 gallon range. Their layered media combines mechanical capture with activated-carbon adsorption, making the cartridge relevant for routine filter maintenance and for tanks where fish waste, debris, odor, or yellow-looking water are concerns.

Which small fish tank filters does this refill fit?

The cartridge is a replacement for Tetra Small Filter Cartridges S Size and fits many brands of Small HOB filters. The listed alternatives are the imagitarium B/C filter and the NuWave Betta Fish Tank filter media cartridge. Its dimensions are 4 × 2.2 in (10.16 × 5.59 cm), so compare the cartridge size and filter type with your existing setup before choosing.

• Made for filters serving 3–10 gallon (11.4–37.9 L) tanks.
• Compatibility includes the named Tetra, imagitarium, and NuWave applications.
• Check that your filter takes a small cartridge of the stated size.

How does the three-layer cartridge filter aquarium water?

Two layers of microfiber cotton absorb solid impurities, including debris and fish waste, while an inner activated-carbon layer absorbs odor and discoloration. This combination is designed to reduce fishy smell and improve yellow water, supporting clearer water for viewing fish. It provides both particle capture and carbon filtration in a single replacement cartridge.

• Double-layer microfiber cotton targets visible solid impurities.
• Activated carbon targets odor and discoloration.
• The cartridge brings both media types together in its three-layer design.

When should I replace the cartridge, and how many are included?

Replace a cartridge every 3 to 4 weeks if water flow is reduced. The pack contains 12 refills and is presented as a one-year supply. Installation and replacement are designed to be convenient, without requiring your hands or fingers to get wet.

• Use reduced water flow as the stated replacement cue.
• Each pack contains 12 replacement cartridges.
• Refills are intended for ongoing filter maintenance.

These ShuRex refills suit fish keepers with a compatible small HOB or other listed small-tank filter who want a single cartridge combining microfiber cotton and activated carbon. They are sized for the stated small-filter applications, rather than being a universal fit for every aquarium filter. The defined cartridge dimensions and named compatibility options help match the refill to the existing filter.

Read our guide: Aquascaping a freshwater tank: substrate, stone, wood and light