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Apart from the zip, the Guppyfriend Washing Bag is made entirely of polyamide 6.6. The material is untreated, undyed and contains no additives. The fabric is made of monofilaments. These are more like sticks than threads and do not lose any fibres themselves.

The Guppyfriend Washing Bags are made of polyamide 6.6. This is a high-tech material and is particularly tough and resistant to alkalis. The fabric itself doesn't shed any microplastic fibres because it is made of monofilaments. These are more like stable sticks than threads, which are made from several fibres and are typically used for textiles. The binding tape consists of long staple fibres. Even if these should become detached from the bond, it is unlikely that they will break off.

During the washing process, all garments lose fibres. The fibres break from the structure of the fabric due to mechanical stress and abrasion. The broken fibres are typically 50 µm to 15 mm long and usually no thicker than 10 µm. 1µm = 0.001 mm or about 0.000039 inch. They could theoretically slip through the small openings of the Guppyfriend Washing Bag. But they do not. To get through the opening, the fibre would have to poke vertically through the fabric. However, due to the water in and around the bag and the movement, the fibres are never positioned vertically, but always slightly bent. Therefore, they cannot pierce through the mesh. Even if a fibre should stick out of the fabric, it will be pushed back into the bag.

At the moment we offer the Guppyfriend Washing Bag in the standard size M, which is 20 x 29 in (50 x 74 cm). According to our tests, the Medium bag is the most effective size for household use. In a larger bag, more microfibres would break off due to the greater friction. For larger amounts of laundry, it therefore, makes sense to use two medium bags instead of one large one. In addition, there should still be enough space in the laundry drum to wash a few loose (non-synthetic) laundry items in addition to the Guppyfriend. This will prevent any possible imbalance. As soon as other sizes are available we will inform you on our website and social media channels.

The Guppyfriend Washing Bag was tested over a period of three years by scientific institutes, universities, representatives of the outdoor and textile industry, as well as retailers. These tests serve as a basis for offering the Guppyfriend Washing Bag as a temporary solution against microplastic pollution. In particular, we have tested with the following scientific and independent institutes:


• German Textile Research Centre North-West, DTNW

• Fraunhofer Institute UMSICHT

• University of California at Santa Barbara as part of the Patagonia research programme.


The Guppyfriend Washing Bag prevents fibre loss during washing in two ways:

1. The Guppyfriend Washing Bag drastically reduces the number of fibres that break off.

Tests by the Fraunhofer Institute UMSICHT showed on average:

a) 79% with partly synthetic clothes

b) 86% with completely synthetic clothing. Thus, the clothing can be worn much longer.

2. Plastic fibres that break off during washing are retained in the bag and thus do not pollute the wastewater. The fibres were retained by over 90% - in most cases 100% - in all tests. Nanoparticles, mostly residues from production, which can be found especially on cheap textiles, cannot be retained by the washing bag.

Other test results:

• No toxic residues were found on the product.

• The bags can withstand 50 household washes according to ISO 6330 without damage and do not release any microplastic particles into the water themselves (Note: when used correctly, the Guppyfriend Washing Bag can also be used beyond the tested number of 50 washes).

• Cleanliness after washing: Blood, ketchup and chocolate are washed out without any problems. The washing effect of skin grease and clay is sufficient.

• The number of broken fibres depends on the washing conditions and the clothes themselves.

In summary:

The Guppyfriend Washing Bag significantly reduces fibre breakage. The fibres that break off during washing are retained in the bag. The clothes become clean and - if the wash bag is used correctly - it can be used for a long time to keep microplastics out of our rivers and oceans. Click here for the test results.

The profits from the sale of the Guppyfriend Washing Bag go to the NGO STOP! MicroWaste and enable the realisation of the STOP! Plastic Academy. In the "Train the Trainer" programme of the STOP! Plastic Academy we do workshops for partners, consumers and educational institutions to raise awareness on (micro)plastic pollution. The following measures are supported by the profits from the washing bag:


• Information events and material: what can be done to avoid micro plastics beyond the washing bag?

• Making the findings from our countless washing tests available to the textile industry in order to establish better yarns and manufacturing techniques that noticeably reduce microfibre discharge from clothing.

• Expanding the Stop! Plastic Academy, lectures on microplastics at schools and universities.

• Initiation and support of local activities, so-called Stop! stations, to avoid single-use plastic.

• Research into new, pragmatic solutions to reduce microfibers.

More information about the STOP! Plastic Academy can be found at


We developed the Guppyfriend to help reduce the amount of microplastic fibers entering the environment. These break off, for example, when washing synthetic textiles (polyester, acrylic, nylon, etc.). It therefore makes sense to wash particularly these textiles in the Guppyfriend. Fleece jackets, sportswear and outdoor clothing are often made entirely or to a large extent of synthetic fibers, but most other garments also contain a certain amount of synthetics. You can check the care label to see what your garments are made of.

However, clothes made of pure cotton and wool can also be washed in the Guppyfriend Washing Bag, because textiles made of natural materials also lose fibers. Washing in the Guppyfriend significantly reduces fibre breakage and thus protects your clothes from wear and tear. You can enjoy your clothes much longer - another sustainable advantage of the Guppyfriend Washing Bag.

By the way: Unfortunately, synthetic fibers may even be present in clothes if they are not indicated on the care label. The rules for listing the components on care labels vary widely, thus a jumper labelled as 100% wool may contain up to 10% of synthetic fibers.

To protect your clothes and for a good wash result, we recommend using a liquid detergent, ideally made from natural ingredients. Washing powders often contain abrasive particles that cause more fibre breakage and can leave deposits on your laundry. But whether you use washing powder or liquid detergent, in both cases it is important to pay attention to the dosage. Too much detergent damages your clothes and the environment.

Only natural detergents without synthetics, such as abrasive particles, gel and skin-forming agents, gums and silicones, opacifiers, acrylates and cross-polymers are not problematic. If you use washing powder, please make sure that it does not contain any liquid plastics or rubbers (xanthan gum) or abrasive particles and that the detergent is well dissolved before it gets onto the laundry.

Since liquid detergent is mainly sold in plastic packaging, you can also fill your own liquid detergent in many zero-waste shops, which of course improves the eco-balance even more.

By the way: The Guppyfriend also works with washing eggs or washing nuts. However, any solid object washed with the clothes will cause significantly more fibers to break. We can therefore not recommend the use of a wash egg or wash nuts - even if they are used with good intentions - as they lead to more plastic in the oceans.

In our tests, the Guppyfriend was washed at a maximum temperature of 40°C. Therefore, we do not recommend washing hotter than 40°.

In general, the warmer you wash, the shorter the life of your clothes. You can find more washing tips in our washing guide “Wash better”.

When washing with the Guppyfriend Washing Bag, an imbalance can occur during the spin cycle. To prevent damage to the washing machine, the spin cycle is often automatically stopped or the speed reduced. This can result in your laundry coming out of the washing machine very wet.

To avoid this, it is important to always put additional garments without any synthetic fibers into the washing drum when using the Guppyfriend washing bag. You can also add another filled washing bag. This prevents an imbalance and your washing machine should spin as usual.

No. During the drying process, just what is not supposed to happen happens: Due to static charging, the broken microfibres pierce trough the bag and end up in the laundry drum and ultimately in the environment.

The reason for this is that the electrostatic reaction of round plastic material (such as synthetic clothing and the round nylon monofilaments of the Guppyfriend laundry bag) creates a magnetic field. Broken fibres are attracted and orientate themselves at a 90° angle to the mesh of the Guppyfriend Washing Bag. Aligned in this way, they can pierce the material and go straight through the mesh. In the washing machine, there is water in and around the bag and the broken fibers lie at various angles on the net, so they cannot pierce through it.

Please dispose of the collected microfibers in the residual waste. It is best to collect and dispose of the collected fibers in a closed container. This reduces the chance of the small and very light synthetic fibers being blown away during waste collection and to end up in the environment.

Microfibers do not belong in recyclable waste (yellow bin, yellow bag, green dot) because they cannot be recycled.

By the way: In Germany, residual waste is used to generate electricity and does not end up in landfills. The exhaust gases from waste incineration are filtered and 99% of them are non-toxic. If you don't live in Germany, you can check the Waste Atlas here to see what happens to the waste in your region.

It's perfectly normal if you don't find any microfibers at first. They are very small and often transparent, so they are sometimes difficult to find with the naked eye, especially in a wet bag.

In addition, the Guppyfriend Washing Bag has been designed to prevent microfiber loss at source. Due to the smooth surface and structure of the material, fewer microfibers break off during washing. This ensures that your clothes are protected, pilling is avoided and fiber loss is reduced. According to a test series by the Fraunhofer Institute UMSICHT, synthetic clothing loses on average 86% fewer fibers compared to washing without the Guppyfriend Washing Bag. The microfibers that do break off accumulate over time. You are most likely to find them in the corners or at the hem.

By the way: The number of fibers that break during washing depends on the type of clothes and the way you wash them: very new or very old clothes tend to lose more microfibres. The higher the temperature, the more likely it is that microfibres will break off. The softer the fabrics, the fewer fibres will break off, etc.

You can find more washing tips to reduce microplastic pollution in our washing guide “Wash better”.

The Guppyfriend Washing Bag withstood the 50 washes of our independent tests flawlessly. However, if you follow our instructions for use, you can use your bag for many more wash cycles. After a few washes, the washing bag won't look like new, but it will still do its job perfectly. In fact, the majority of our early adopters still use their first Guppyfriend Washing Bag from 2017 today.

The Guppyfriend Washing Bag is made of untreated polyamide 6.6 and is designed to be completely recyclable when you remove the zip. The best thing to do is to dispose of it in the recycling bin and thus introduce it into the recycling system. To do this, separate the cover with the zipper from the fabric. In Germany, the fabric belongs in the yellow bin (yellow bag, green dot) and the zipper in the residual waste.

By the way: Recycled material cannot (yet) be used for high-tech fabrics like the material of our Guppyfriend Washing Bags. Unfortunately, old Guppyfriends cannot yet be used for the production of new Guppyfriends. Therefore, it does not make sense to return your old Guppyfriend to us - especially with regard to the resources needed for shipping. It is best to return your old Guppyfriend to your local recycling centre, where it can be recycled with identical materials.


Microfibers are so small that they would immediately clog permanently installed filters, quite literally in a matter of seconds. The microfibers that collect on the filter would be forced through the filter into the wastewater due to the high water pressure. To avoid this, the filter would have to be constantly replaced or cleaned.

We have developed a working prototype for a washing machine filter and other companies are also working on such solutions. However, it will take some time before these filters are effective and permanently functional. Until then, the Guppyfriend Washing Bag is a practical and effective way to reduce plastic pollution in rivers and oceans and raise awareness about the problem.

Washing machines are usually unable to filter out the microplastic fibers in our textiles that break off during washing. Thus, the fibers enter the sewage treatment plants with the household wastewater. However, countless particles escape the filter systems and end up in our environment. According to a study by the University of California in Santa Barbara, on average 60% - 99% of microplastic particles are filtered out of the water. In Germany, only 20 out of about 10,000 sewage treatment plants have the so-called purification stage 4, whose main aim is to rid our wastewater of medicine residues.

Microplastic fibres are particularly difficult to filter out. Due to their shape and floating properties, they pass through the filter systems much more frequently than other types of microplastics such as pellets, so-called microbeads from cosmetics and other plastic fragments.

But even if they are filtered out, the plastic particles often end up back in the environment with the sewage sludge. If the sewage sludge is not incinerated, it is used as fertiliser on fields. From here, the microplastic particles bound in the sewage sludge make their way back into our oceans.

So-called combined sewer overflows are another problem. They serve to relieve the sewage system in the case of heavy rain. In order to prevent backwater in households during heavy rainfall, the wastewater flows through the sewers untreated when the volume of water is high.

By the way, the wastewater from the gullies does not pass through a sewage treatment plant, but flows mostly unfiltered into our waters. The microplastic particles from tyre and shoe sole abrasion, as well as microplastic fibres found in the air and in sewage sludge, therefore pollute our environment directly.

For technical reasons, the filtering possibilities of sewage treatment plants are unfortunately not sufficient to prevent the pollution of the oceans by microplastics. However, by rethinking our buying habits and mindful washing behavior, everyone can contribute to reducing the amount of microplastics entering the environment.