Red Sea Filter Media Bags

• Drawstring closure – fills, ties and reopens without clips, so you can top up or swap media without replacing the bag.
• Two per pack – enough to run one and rinse one, which is how most people actually use them.
• Reusable – Red Sea lists reusability as a feature. Rinse and refill rather than discard.
• Takes any loose media – carbon, GFO, phosphate remover, resins. Red Sea's own wording is that it suits all types of aquarium filter media.
• The bag Red Sea ships with REEF-SPEC Carbon – if you have used their carbon, this is the bag it came in.

Some overseas dealers list this bag as 14 x 25 cm and as holding 1000 mL. Red Sea's own figure is 12.5 x 25 cm, and Red Sea publishes no volume, so that is what this page states.

This is not a model-specific part, and we are not going to pretend it is. Red Sea publishes no compatibility list for R37401 – no REEFER generation, no MAX model, nothing. It does not appear in any Red Sea manual, sump drawing or exploded parts diagram. It is a loose drawstring bag with no holder interface.

So the honest answer to "will it fit?" is dimensional. A 12.5 x 25 cm bag will sit in any sump chamber, media compartment or filter basket that has room for it. Measure the space you want to put it in. If a bag that size fits, this bag fits.

For reference, Red Sea's Filter Media Cup (part 42177) holds one litre of media, is described by Red Sea as suitable for REEFER and MAX systems, and ships with a media bag included. That is a claim about the cup, not about this bag, so do not read it as a fitment guarantee for R37401.

The most common mistake with this part is buying it when you actually wanted a micron filter bag. They are different products with different jobs.

Red Sea publishes no micron rating for R37401, only that it has an ideal mesh size for aquarium filter media. If your setup depends on a specific pore size, this is not the part – buy a rated micron bag instead.

• Rinse in old tank water or dechlorinated water, never under a hot tap.
• Wash the bag out when you change media – a clogged bag chokes flow through the media inside it.
• Red Sea publishes no replacement interval. Replace when the mesh thins, the seams give, or the drawstring stops holding.
• Do not overfill. Media needs water moving through it, not packed around it.

Suitable for

• Activated carbon, GFO and phosphate removers
• Nitrate and organic removal resins
• Any loose granular media in a sump chamber or filter basket
• Freshwater and marine systems alike

Not suitable for

• Rated mechanical filtration. No published micron rating means no guaranteed particle retention.
• Use as a filter sock in a sock holder. It has no collar or ring to seat in one.
• Very fine powdered media, which will wash straight through a mesh of unstated aperture.

• Red Sea DIY Net Cover – the other genuine Red Sea accessory most REEFER and MAX owners get around to eventually.
• Red Sea Marine Care Nitrite/Nitrate Test Kit – measure the nitrate before and after you run a resin, or you will never know if it worked.
• Red Sea Marine Care Multi Test Kit – the routine four parameters for a system running chemical media.
• Red Sea Coral Pro Salt – for the water changes that go alongside media changes.

Red Sea's warranty expressly does not cover normal wear and tear, or items that have a limited natural life or are consumable – Red Sea names filter socks and sponges among its examples. A media bag is a consumable and is not covered for wear. Any manufacturer warranty is in addition to your rights under the Australian Consumer Law and does not limit them.

Standard freight. No dangerous goods or oversize handling applies.

What is the Red Sea part number for these media bags?

R37401. Red Sea's own product page does not print the part number, but it is the code used by Red Sea's spare parts system and by Red Sea distributors for the 2-pack drawstring media bag.

Which Red Sea systems do these bags fit?

Red Sea does not publish a model compatibility list for this bag, because it is a universal drawstring bag rather than a fitted part. At 12.5 x 25 cm it will sit in any sump chamber, media compartment or basket with room for it. Measure the space before ordering.

What micron are Red Sea filter media bags?

Red Sea does not publish a micron rating for R37401 – only that the mesh size suits aquarium filter media generally. If you need a rated pore size, use Red Sea's micron filter bags instead: R42195 at 100 micron, or R42196 and R42197 at 225 micron.

How many bags come in a pack?

Two. Red Sea's own specification reads 12.5 x 25 cm, 2 units.

Can I reuse them?

Yes. Red Sea lists the bag as reusable. Rinse it out at each media change and replace it when the mesh thins or the drawstring gives up.

Can I use these in a freshwater tank?

Yes. It is an inert nylon bag holding whatever media you put in it, so the water type makes no difference to the bag itself.