Zip Bag Medium 12.5" x 5.5" — 16 Mesh Filter Bag with Zipper | Seachem

The Seachem Medium Zip Bag (12.5" x 5.5" / 32 x 14 cm) is a medium-mesh (16 mesh) filter bag with a corrosion-resistant zipper, designed to hold medium and large filter media. It easily accommodates 1 liter of media, and its 16 mesh provides an excellent balance between media retention and water flow. Compatible with a wide range of media, including PhosGuard, MatrixCarbon, denitrate, and Matrix. Made of PVC with durable stitched seams, it closes securely without strings or ties.

Main advantages

• Dimensions 32 x 14 cm (12.5" x 5.5") — easily holds 1 liter of filter media
• Medium mesh 16 Mesh — excellent balance between media retention and water flow
• Corrosion-resistant zipper — no strings or ties, quick opening and closing
• PVC material with durable stitched seams
• Resistant to bleach, caustics and acids

Use in reef and marine aquariums

The Medium Zip Bag is the versatile filter bag in the Seachem range, suitable for the widest range of chemical and biological filter media. Its 16-mesh construction retains medium-sized media such as PhosGuard, MatrixCarbon, denitrate, and even Matrix, while offering a higher water flow rate than the Small Zip Bag (25 mesh). Ideal for use in cartridge filters, media chambers, and sumps. For very fine granular media such as PhosNet or PhosBond, the Small Zip Bag (25 mesh) is recommended. For fine resins such as Purigen, use the Seachem The Bag (180 microns).

Technical specifications

• Dimensions: 32 x 14 cm (12.5" x 5.5")
• Mesh size: 16 Mesh (medium)
• Closure: corrosion-resistant zipper
• Material: PVC
• Seams: sewn
• Capacity: 1 liter of media
• Resistant to: bleach, caustics, acids

Media compatibility

• Seachem PhosGuard (aluminum oxide)
• Seachem MatrixCarbon (spherical activated carbon)
• Seachem SeaGel
• Seachem de*nitrate
• Seachem Renew
• Seachem Matrix
• Seachem Zeolite

Do not use with fine resins (Purigen, CupriSorb, HyperSorb) — use Seachem The Bag. For very fine granular media (PhosNet, PhosBond), the Small Zip Bag (25 Mesh) is recommended.

Comparison of Seachem filter bags

• The Bag (5" x 9.5"): 180-micron superfine mesh, welded seams — ideal for thin resins (Purigen, CupriSorb) and all media
• Small Zip Bag (12.5" x 5.5"): 25 Mesh, stitched seams — ideal for PhosNet, PhosBond, and fine granular media
• Zip Bag Medium (12.5" x 5.5"): 16 Mesh, stitched seams — the most versatile, PhosGuard, MatrixCarbon, denitrate, Matrix
• Zip Bag Large (19" x 17"): 8 Mesh, stitched seams — ideal for bulky Matrix and Pond Matrix bags

Instructions for use

Place the desired filter media in the bag and close it with the corrosion-resistant zipper. Position the bag in the cartridge filter, media chamber, or sump to maximize water flow through the media. Do not overfill—the media should rest loosely enough to allow water to circulate.

Why choose the Zip Bag from ReefSolution?

The Medium Zip Bag is the most versatile filter bag in the Seachem range, compatible with the widest range of media. Its corrosion-resistant zipper makes regular media replacement easy. Combine it with Seachem MatrixCarbon for chemical filtration, Seachem PhosGuard for phosphates, or Seachem de*nitrate for denitrification.

Frequently Asked Questions

What is the difference between the Medium Zip Bag and the Small Zip Bag?

Both have the same dimensions (12.5" x 5.5") but a different mesh size. The Medium has a 16 Mesh (more open) mesh compatible with a wider range of media, including denitrate and Matrix. The Small has a 25 Mesh (finer) mesh for fine granular media such as PhosNet and PhosBond.

Can the Medium Zip Bag contain Purigen or CupriSorb?

No. The 16 Mesh will allow thin resins to pass through. Use the Seachem The Bag with its superfine 180-micron mesh and welded seams for Purigen, CupriSorb, and HyperSorb.

Is the Medium Zip Bag the most versatile bag in the range?

Yes. Its 16 Mesh is compatible with the widest range of Seachem media, from MatrixCarbon and Matrix to PhosGuard and denitrate. It's the default choice for most chemical and biological filtration applications.