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Last update: April 7, 2021

The 2 best mesh bags for holding your filter media (18 tested!)

Quick, name a piece of aquarium equipment!

I’m 99.9% certain you didn’t say filter media bag.

My point is that this is likely a product that you won’t even give a passing thought to.

That is unless you have ever had to clean Purigen or activated carbon out of your aquarium because your media bag broke.

Yep, choosing a high-quality media bag is important.

Luckily for you, we tested the most popular media bags on the market, so you don’t have to.

If you want to know everything there is about this boring but useful product, you have come to the right place!

What is a filter media bag?

Filter media bag with ceramic rings

Filter media refers to anything you place in your filter that changes the quality of the water flowing through it.

Examples of filter media include:

If you pour any of these media into your filter, it would soon flow through your aquarium and gunk up your tank.

The problem? These media are made up of small pieces, like this activated carbon…

Activated carbon used in a chemical filtration system

Due to the small size and light weight, each individual piece can be lifted up and carried by the water that is flowing through your filter – ending up in your aquarium.

Trust me when I say this:

Scooping out media that has escaped your filter is a pain in the butt!

That’s where a filter media bag comes in.

In canister filters, media bags are used to separate each filter media. For example, by using three separate bags, you could layer ceramic noodles, activated carbon and Purigen in the same filter without them mixing together.

Pretty simple, huh?

You can also buy filter media in pre-packaged bags. The problem? They are sewn shut. So once you need to replace the media, you need to dispose of the entire bag.

It is for this reason that I recommend buying media bags separately. It might cost more initially but will eventually save you money – buying filter media by the bottle is much cheaper in the long run.

What are the different types of filter media bags?

Not all filter media bags are created equally. Below are two things to be mindful of when choosing the right media bag for your filter.

1. Mesh and bag size

Mesh size of a fine and coarse filter media bag close-up

A filter media bag should be large enough to fit in the cavity of your filter.

Remember, the purpose of filter media is for water to flow through it. If the media bag is too small, water will be able to flow around the bag, rendering the media useless.

I recommend buying a filter media bag that is just bigger than the cavity of your filter.

But it’s not just the size of the bag that you have to worry about, but also the size of the mesh.

You see, there are many different types and brands of filter media. Some are big and chunky, like ceramic rings, while others are frustratingly fine, like Purigen.

Seriously, check it out…

Close-up on Seachem Purigen filter media

It’s this fine filter media that’s the problem. If the holes in the mesh are too large, the media will escape the bag and flow into your aquarium, making a mess that needs to be cleaned up.

The fine filter media bags I recommend later this guide are all capable of holding Seachem Purigen!

But a fine mesh has its drawbacks. For one, the smaller holes reduce the amount of water that flows over the filter media. You may also find that these bags gunk up or clog quicker. It is for this reason that you should choose a coarser mesh for larger filter media.

2. How it closes

Zipper

Filter media bag with zip opening

Zippers are great. Outside of the water, that is. All the media bags I tested that were “designed for aquarium use” had metal zippers.

The problem? Rust and corrosion.

Every media bag I tested that featured a zipper would eventually rust… Even the ones that were coated with paint. A tiny scratch or chip on this paint was a one-way ticket to rust city.

It is for this reason that I recommend…

Drawstring

Filter media bag with drawstring opening

Ugly but functional. I found the all-plastic design to be the best closing mechanism when it came to filter media bags.

Toss your media in the bag, pull the drawstring closed, and you are done. Simple.

Velcro

Filter media bag with Velcro opening

Velcro was another strong performer. However, I found that over time, pieces of sand and fine filter media would get stuck in the Velcro strip.

Velcro closures on media bags were much less common. In fact, while looking for filter media bags to review, I only came across two brands.

How do you use a filter media bag?

Using a filter media bag is darn simple. Let’s walk you through the steps…

Step 1: Measure your filter

Measuring the opening of canister filter to determine filter media size

The first thing you want to do is measure the opening of your filter – both the length and width of where you will place your filter media.

Write down the measurements so that you don’t forget them!

Step 2: Find an appropriately sized media bag

Measuring a coarse mesh filter media bag to determine its size

Next, you want to take your measurements and find the closest-sized media bag.

Given the wide range of filter sizes, it is unlikely that you will find a media bag that perfectly fits your measurements.

So, what you want to do is find the nearest size, without going under your measurements.

Step 3: Fill your media bag

Filling a filter media bag with bio balls for aquarium

Before you fill your media bag for the first time, wash it in fresh water and don’t forget to treat it with water conditioner!

This will remove any dust and chemicals that were left over from manufacturing – you don’t want any of this stuff in your tank.

Once dry, fill your bag with your filter media. In this case, I am using bio balls.

Step 4: Place your media bag into your filter

Inserting full media bag into canister filter

Turn off your filter and open it. You should see a media tray. It’s here that you want to carefully place your media bag.

Give your media bag a light shake back and forth so that the media evenly spreads throughout the bag.

You want to position your bag so that the water flows through your media without any gaps.

Now, because it’s very likely the media bag you used is larger than your filter, carefully fold or scrunch the edges of your media bag to keep things neat.

That’s really all there is to it. You can now close your filter and turn it back on. See, I told you it was simple!

Best filter media bags

After testing all the main players, including Seachem and Fluval Aquaclear, and other solutions such as beer brewing bags and pantyhose, the following Weco media bags stood out above all others…

Weco filter media bag

Available in a wide range of sizes, from 4″ x 8″ to 12″ x 15″, exceptional quality and at an affordable price, there really wasn’t another media bag that came close.

The fine mesh media bags were more than capable of containing Purigen and other resins without any leaking into the aquarium.

The coarse size worked great for larger media like ceramic noodles and bio balls.

I am so impressed that I will be using these media bags in my tank at home. Highly recommended!

Runner-up…

Pura filter media bags by Magnavore

When it came to offering value for money, nothing was better than the Pura Media Bags manufactured by Magnavore.

While they only come in one size, 6″ x 12″, these Velcro-sealed bags were perfect for keeping Purigen contained and were of exceptional quality.

If you only need a small media bag for your filter, make this your choice!

Conclusion

Okay, so filter media bags are definitely not a product that you will give much thought to.

But if you plan on using lose media in your filter, then this simple mesh bag is going to make your life much easier.

And if you haven’t made the switch to loose media yet, what are you waiting for? You will save money in the long run!

What media bag do you use in your filter? Let me know in the comments below!

Ian Sterling

I've been keeping fish for over 30 years and currently have 4 different aquariums – it's an addiction. I'm here to teach you everything there is to know about fishkeeping.

I also use this site as an excuse to spend lots of money on testing and reviewing different aquarium products! You can find my reviews here.

Comments (15)

Hi Loren,

Thanks for the feedback, it motivates me to create more detailed reviews like this. And, between you and me, it helps me to justify the money I spend on all this gear to my wife!

I bought purigen ultimate filtration bags. 100mL, 100cm,6in. I bought these due to brown algae growing on everything in both of my tanks. I cleaned the tanks ,as well as the live plants of this brown algae. I put 50%new H20 in & the purigen bags. I have a 40 gl. tank & a 10 gl. tank. I put the purigen bags in behind the new filters. One bag in each tank. It’s been about a month now.I still am getting brown algae growing in both tanks. I do make weekly H20 changes. What’s the problem?

Hi Ruthie,

The reason you are not noticing a change is because Purigen isn’t the correct product to use. While it can help control ammonia, nitrites and nitrates, these don’t impact brown algae.

In a newly established tank, brown algae growth is considered normal and will go away on it’s own. If you have an established tank then something else is likely at play.

If you have correctly identified that your algae is brown algae, then it’s possible your water is either high in silicates or phosphates – it is believed that these are used as a food source for silicates and may be present in your tap water.

The first thing I would do is make sure all your water parameters are normal using a good test kit. Making sure your water is “healthy” is always the best place to start.

Next test your water using a phosphate or silicate. If it’s present, you can use a product like Phosguard in your filter to remove these elements. With the food source gone, your brown algae problem should go too. You’ll still need a good filter media bag for your Phosguard, or any other resin you use.

With repeated cleaning and water changes and a bit of luck, you should see your brown algae gradually disappear.

I’m semi new to the hobby (had a 30 gal salty15 yrs ago but so much has changed!) and really appreciate when established hobbyist take their time to share their knowledge and experiences. I’m always looking for reviews on diff products and was happy to find this one for media bags. We all know how costly things can get in the hobby so any help to ensure whatever I’m buying is good quality stuff is so beneficial and I truly value the input! Thanks a bunch!

Hi Cindi,

Thanks for the lovely feedback. I completely agree with you. I shudder to think how much I have spent on fish keeping equipment during my time in the hobby. There is nothing more frustrating than buying something only to discover it doesn’t suit your needs – even something as minor as filter media bags!

Thanks for doing this research!!! I found Purigen a few years ago and it changed my life!! I had been cramming 4 100ml pouches in my filter and I decided I would rather buy in bulk and get one bag for the chamber… I am so happy I found your reviews! Off to buy a bag now….

Hi Jennifer,

Purigen is some great stuff, except when it escapes into your tank. I think you’ll never go back to cramming 4 pouches in again once you have your media bag!

Ty ty ty! I do my own research on everything but, it’s so hard to find reviews that aren’t being “sold ” to you as a review instead of a sales pitch and bias. Ty for your work and honesty. I love this site more an more.

Ian, I’m trying to use Purigen in a biorb tank with round, central filter. I’m already regretting the biorb purchase, but whatever. In your reviews were there any 3″ or more narrow bags roughly 10″ long with fine mesh (180 micron or smaller)? Should I just use toddler stockings? LOL Thanks in advance.

Hi Walter,

I’m sorry you ended up with a biorb tank. I honestly wish these were not sold here. They are very restrictive when it comes to modifying them.

I did come across some narrow sock-like mesh bags that were used in brewing beer that were near these dimensions. Unfortunately, I cannot recall if they would be fine enough to hold in purigen. I have a suspicion that they are not given their purpose. I think the toddler stockings may be your best bet for this unusual size. However, make sure you check the stocking regular for wear. As someone who has had a purigen jailbreak in his tank, it’s not something I would wish on anyone.

If it’s primarily for the removal of tannins, why not use activated carbon instead? It’s significantly larger size will allow you to use a coarser bag. You may even be able to get by with a beer brewing bag for activated carbon as well.

Hi.

If I am floating a media bag in the pond (with polywool and activated carbon) under a waterfall, does it need to be full to the brim with media? I have a large mesh bag and the media i have fills about 2/5 of the bag. Drawstring bag.

I already have other filtration on the go…in pump filters etc

As you can guess, i am using the wool and carbon to clear tannins

Thank you

Hi Gareth,

Fighting tannins in a pond is forever a battle due to the open nature of it and the considerable amount of water they hold. The amount of carbon you would need would entirely depend on the amount of tannins + volume of water. At a point, the size of a pond becomes impractical to remove tannins from – it’s not like an enclosed aquarium.

Hi Ian, First off love your website, full of insight!!! Thanks very much! Secondly, I wanted to share that I have been using the Pura Media bags for Purigen for about a year now and after many bleach soaking regenerations the velcro has finely given up and coming apart. They are great bags, especially for the price and I am considering getting them again, but my experience has been a one year lifespan.

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