Weco Coarse Mesh Zipper Media Bag (4 x 8 in) | Reusable Filter Bag for Carbon & Bio Media

The Weco Coarse Mesh Zipper Media Bag is the simple, reusable workhorse for keeping loose filter media exactly where you want it. Drop in your carbon, ceramic rings, bio-balls, or chunky resin, zip it shut, and place it in your sump, canister, or HOB. Coarse weave keeps water flowing fast — built for larger-media types like activated carbon, biological ceramics, and pelletized media. Browse our full filter media & cartridges or shop maintenance & water care.

What It's For

This is the bag you reach for when you've got chunky media — bituminous or pelletized activated carbon, ceramic bio-rings, bio-balls, lava rock, or coarse-grade phosphate resin. The looser weave on the coarse version lets water rip through the media at full flow rate without the back-pressure you'd get from a fine bag. If you're polishing water with GFO, ultra-fine carbon, or Purigen-style resins, grab the fine mesh version instead — the coarse weave is too open for the smallest media.

Features

How to Use

Fill the bag with your chosen media — typically 1 to 1.5 cups for a 4 × 8 bag depending on media density. Zip it fully closed, rinse the bag under fresh water to flush dust, and place it where water will flow through it: a sump chamber, canister tray, or HOB media basket. Rinse the media monthly to clear gunk, and replace the media (not the bag) per its rated lifespan — typically 4–8 weeks for carbon, longer for biological media.

Specifications

Recommended Media to Pair With

• Seachem Matrix Carbon — premium activated carbon for freshwater & saltwater
• Red Sea REEF-SPEC Carbon — reef-grade carbon for saltwater systems
• IceCap Bio-Sphere — dense ceramic biological filter media
• Aquaforest Life Bio Media — freshwater biological media
• Browse the full filter media collection

FAQ

Coarse or fine — which do I need?
Coarse is for chunky media (carbon pellets, ceramic rings, bio-balls). Fine is for powders and tiny granules (GFO, ultra-fine carbon, Purigen-style resin). When in doubt, hold the media in your hand — if you can see individual chunks, coarse is fine. If it looks like sand or powder, get the fine bag.

How long does the bag last?
The bag itself outlasts the media inside. With monthly rinsing it typically lasts a year or more before the mesh starts to fray. Replace the media on its own schedule and reuse the bag.

Is the nylon safe for reef tanks?
Yes — inert nylon mesh is reef-safe and won't leach anything into the water column. Rinse before first use to clear any manufacturing dust.

Will it fit my filter?
The 4 × 8 bag fits most sumps, canister media trays, and HOB media chambers. For small canister cartridge slots, measure first — Weco also makes smaller bags.