Fish Tank Filter Supplies

The core fish tank filter supplies you need are filter media (mechanical, biological, and chemical), replacement cartridges or pads if your filter uses them, a brush for cleaning filter tubing and impellers, and a way to dechlorinate water used when rinsing media. Beyond those basics, there are optional supplies like filter socks, polishing pads, and specialty resins that help you dial in water quality for specific tanks.

This guide covers every category of filter supply, which products are worth buying, how often to replace them, and how to avoid the most common mistakes hobbyists make with filter maintenance.

The Three Types of Filter Media

All aquarium filtration works through three mechanisms, and your supply list flows from understanding them:

Mechanical Filtration

Mechanical media physically traps particles: uneaten food, fish waste, plant debris. Filter sponges, filter pads, and filter floss all fall into this category.

Filter sponges are reusable: you rinse them in old tank water (never tap water, which kills beneficial bacteria) every 2 to 4 weeks and they last for years. The Fluval Foam Pad for the 207/307 canister and the Aquaclear foam inserts are popular examples that fit their respective filters.

Filter floss (also sold as polyester aquarium padding or Dacron) is a fine white fibrous material used as final mechanical filtration. It polishes water to crystal clarity by catching fine particles the sponge misses. It's cheap ($5 to $8 for a large roll) and you replace it every 2 to 4 weeks when it's visibly brown and packed with waste.

Filter socks are mesh tubes placed over the inlet of sump filters or canister returns. They catch large debris before it enters the sump. You wash them in the washing machine (no detergent) or rinse them out every 1 to 2 weeks.

Biological Filtration

Biological media provides surface area for beneficial bacteria (Nitrosomonas and Nitrospira) that convert toxic ammonia to nitrite and then to nitrate. This is the most important filtration stage and the one you must never disrupt carelessly.

Biological media options include: - Ceramic rings (Fluval Bio-Rings, Marineland Bio-Filter Balls): inexpensive, large surface area, lasts indefinitely - Sintered glass media (Seachem Matrix, Eheim Substrat Pro): higher surface area per unit volume, good for small filter chambers - Plastic bio-balls: less surface area than ceramic but nearly indestructible - Lava rock: cheap and effective, just look at it for sharp edges that can damage fish or impellers

Biological media should rarely be replaced. It only needs replacement if it physically disintegrates (rare with quality ceramic media) or becomes so clogged with detritus that flow through it stops.

Critical mistake to avoid: Never clean all your biological media at the same time, and never clean it in tap water. The chlorine in tap water kills the bacteria. Rinse only in old tank water from your water change bucket, and only rinse one section at a time, leaving other sections undisturbed.

Chemical Filtration

Chemical media removes dissolved compounds: chlorine, chloramines, medications, tannins, ammonia spikes, and specific pollutants.

Activated carbon is the most common chemical media. It removes odors, discoloration, and trace compounds from the water. Carbon is single-use: it adsorbs until full and then stops working, typically in 4 to 6 weeks. After that it can leach some absorbed compounds back, though this is less of a concern than it used to be thought. Replace carbon every 4 to 6 weeks or after medicating (remove before adding medications, add fresh carbon after treatment ends to clear medication residue).

Seachem Purigen is a synthetic polymer media that removes nitrogenous waste compounds. It's rechargeable: you soak it in a bleach solution per the instructions, rinse thoroughly, and it returns to full capacity. A bag lasts 1 to 3 years with proper regeneration. It's more expensive upfront ($15 to $30 for 100-250mL) but cheaper per use than regular carbon.

Specialized resins: Seachem PhosGuard removes phosphate and silicate (good for controlling algae or diatom blooms). Seachem Cuprisorb removes copper (critical if you've dosed copper-based medication). These are specialty supplies you buy when you have a specific problem.

Filter-Specific Supplies by Filter Type

Hang-On-Back Filters (HOB)

HOBs like the AquaClear 50/70/110, Marineland BioWheel, and Seachem Tidal use proprietary cartridges or modular media baskets.

AquaClear filters use three-stage media: foam sponge, ceramic rings (Aquaclear Biological Media), and activated carbon pouch. The foam lasts years with rinsing, the ceramic rings last indefinitely, and the carbon pouch should be replaced every 4 to 6 weeks (or omitted and replaced with more biological media). Total media replacement cost runs $10 to $15 per year for a typical AquaClear 50.

Marineland filters use a rite-size cartridge (carbon in a mesh bag) designed to be replaced monthly. These are the most expensive ongoing cost in HOB filtration at $3 to $5 per cartridge. You can save money by buying Marineland replacement cartridge refills and repacking old cartridge frames with fresh carbon.

Canister Filters

Canisters like Fluval 207/307/407, Eheim Classic, and SunSun CF filters have multiple media trays you customize.

You'll need: - Mechanical pads (replaced every 4-8 weeks depending on bioload) - Biological media (lasts years; just rinse occasionally) - Carbon or Purigen in the chemical tray (replaced monthly or regenerated) - Impeller cleaning brush (a narrow bottle brush fits most impeller chambers) - Spray bar or outlet tubing cleaning brush

Fluval sells a complete cleaning kit (the Fluval Aquarium Maintenance Kit) for about $8 to $12 that includes brushes for the spray bar, impeller, and filter tubing.

Sponge Filters

Sponge filters only need the sponge itself plus an air pump and tubing. Replacement sponges for popular models like the Hikari Bacto-Surge or Aquaneat double sponge filters cost $5 to $10. The sponge should be rinsed in old tank water every 3 to 4 weeks.

For a broader look at complete filter setups, check out Best Aquarium Equipment.

Filter Supply Replacement Schedule

Essential Filter Maintenance Tools

Turkey baster or pipette: Sucks up mulm from substrate near filter intakes without disturbing the tank. Cheap ($3 to $5) and used constantly.

Cleaning brushes: A long thin brush for impeller chambers and a medium brush for spray bars. Fluval, Python, and generic aquarium brush sets all work. About $8 to $12 for a complete set.

Python No Spill Clean and Fill: While not strictly a filter supply, this gravel vacuum system (about $30 for the 25-foot version) makes water changes fast enough that you do them regularly, which reduces filter maintenance needs.

Dechlorinator: Essential for any new water added to a tank with an active filter. API Tap Water Conditioner (treats 200 gallons for $4 to $5) or Seachem Prime (treats 500 gallons for $7 to $10). Prime is the better value at any volume.

You can find reviews of complete filtration setups and media comparisons at Top Aquarium Equipment.

FAQ

Do I need to use carbon in my filter? No. Carbon is optional. In a healthy, well-maintained tank with regular water changes, carbon adds little benefit beyond removing slight discoloration and odors. Where it's genuinely useful is in new tanks to clear any chemical off-gassing from new decorations, after treating with medication, or in tanks with driftwood where tannin removal is desired. Many experienced hobbyists replace carbon slots with more biological media.

Can I use tap water to rinse my filter media? No. Even if you treat tap water with dechlorinator before it goes in the tank, rinsing filter media directly in tap water exposes the beneficial bacteria colony to chlorine or chloramine that can significantly reduce bacterial populations. Always use water from your tank's water change bucket.

How do I know if my filter media needs replacing? Mechanical media (sponge, floss, pads) is ready for replacing when it doesn't recover its shape after squeezing or when flow through the filter noticeably drops despite cleaning. Biological media almost never needs replacing unless it physically crumbles. Carbon needs replacing on schedule (4-6 weeks) regardless of appearance since it loses adsorption capacity invisibly.

Why does my filter smell even after cleaning? Trapped organic waste in the media, tubing, or impeller housing. The most commonly missed spot is the impeller chamber: fish waste and biofilm build up around the impeller and create an anaerobic pocket that smells like rotten eggs (hydrogen sulfide). Clean the impeller chamber with a brush every 1 to 2 months, and clean the intake and output tubing at the same frequency.

Summary

The filter supplies you actually need come down to replacement mechanical media (filter floss and sponge pads), biological media that lasts for years without replacement, and a chemical option like carbon or Purigen refreshed monthly. Add a cleaning brush set and an impeller brush for maintenance, and a good dechlorinator for water changes. For most hobbyists, yearly filter supply costs run $20 to $40 for a standard canister or HOB filter. The biggest mistake is replacing biological media too often or rinsing it in tap water, which crashes the beneficial bacteria colony and causes a re-cycle.