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How are fish dyed?

When dyed fish were first imported into the UK from the Far East in the 1980s many were unaware of how they came to be so brightly coloured.

We think the process is cruel and unethical and we're asking shops to sign a pledge saying they won't sell them.

What are dyed fish?

Dyed fish are those which have been artificially coloured to make them more appealing to some fishkeepers. Most are now believed to be cruelly injected with pigments. Many claim that others are fed on dye-rich foods, however, although this is possible there is little evidence to support this. Indeed, recent evidence regarding the production methods for coloured Parrot cichlids, which were once believed to be colour-fed, has since shown that the fish are injected.

Why dye fish?

Some suppliers in the Far East, and Taiwan and Thailand in particular, seem to be under the mistaken impression that fishkeepers like these gaudy fish.

This Corydoras has undoubtedly been injected with dye.

They're imported, often mistakenly by dealers, and sometimes sold on to an unsuspecting public who wouldn't have even imagined that they acquired their odd colours through an artificial process. Some are also sold by dealers who don't see the process as unethical.

It's worth pointing out that this is far from common in the aquarium hobby and only affects a tiny proportion of the fish sold. Most fish are sold with their natural colouration, or they're the result of line breeding which has selected individuals with the best colours as brood stock.

How do dyed fish get their artificial colours?

There is lots of speculation about how different varieties of dyed fish come to get their colours. These are the facts: Dyed glass fish, and other species that bear a distinctive fluorescent stripe of dye have been photographed being injected with brightly coloured acrylic paints.

In February 2006, Matt Clarke wrote an article explaining how one fish supplier in Hong Kong was offering fish with words, logos and patterns on their flanks which had been applied using a dye laser. There is evidence from the fisheries science field that this can cause damage to the fish. Several fish, including Kaleidoscope gouramies, are believed to be produced using this technique.

Kaleidoscope gouramies are probably produced using the dye laser technique.

In May 2006, we received photographic and written evidence to show that coloured Parrot cichlids are produced by injecting them with dyes and food colourings at multiple sites on the body. These were previously believed to have been fed on special diets containing high levels of colourant chemicals, or kept in water containing extremely high levels of dye. Both methods had been demonstrated in the fisheries science field and have previously been used for tagging fish.

Some believe that others may also be "dipped" in various chemicals and that special dyes or paints are used to stain the actual skin of the fish. However, we haven't seen any hard evidence to substantiate this.

What about colour foods?

Fishkeepers have been enhancing the diets of their fish with foods containing naturally occurring carotenoid pigments, such as astaxanthin and canthaxanthin, for many years. These pigments are found in many organisms, ranging from krill to spirulina, and when fed in large quantities over extended periods can enhance the fishes' natural colouration. Many manufacturers also isolate these pigments and add them to standard foods and to colour-foods, designed specifically for enhancing colour. There's absolutely nothing wrong with this. Many of these carotenoids act as anti-oxidants and research has shown that they have health benefits.

There's some debate over how these Tiger barbs are dyed.

It is true that such colour-fed fishes can fade if the levels of pigments are not sustained. Heavily colour-fed fish should be fed a special colour food if you wish to sustain their bright colouration. There are no welfare issues relating to this form of colour-feeding.

However, there are also fish on sale in the industry, such as green, blue and purple parrot cichlids and tetras, which also have very deep colouration. These were believed to be produced through feeding a chemical enhanced diet. However, it has recently been confirmed that these are injected with dye. Many examples of fish sold as colour-fed, may in fact represent those that have been injected with coloured dyes.

And genetically modified fish?

First of all, the definition of what is genetically modified is very important. Genetically modified organisms (GMOs) are produced by inserting a specific gene from one species into the DNA of another at an embryonic level. The technique has been used to create pinkish-red danios and yellow-green Medakas which glow under appropriate lighting. The green forms contain a gene which encodes the green fluorescent protein (GFP) from a jellyfish while the pink form contains an additional gene from a coral which produces red reef coral fluorescent protein (RFP).

Glofish are true genetically modified fish and are not dyed in any way.

Scientific evidence has not shown any significant environmental or welfare issues relating to the sale of genetically modified fishes. However, as this article outlines, the global aquarium industry, including the UK's Ornamental Aquatic Trade Association (OATA) opposes the sale of such fish.

A license from Defra is required to legally sell or house genetically modified organisms in the UK. Defra tells us that no licences have been issued in the EU, or the UK. As a result, any such fish on sale in the UK at present are highly likely to be illegal. While we do not have any real issues with genetically modified organisms (there are few, if any, significant welfare issues) we would prefer not to see such fish sold.

Are Parrot cichlids being dyed?

Many experts originally believed that these fish actually received their artificial colours via special feeds which contain excessive levels of artificial pigments, or through keeping them in water containing high levels of dye. As a result, they were considered to be slightly more acceptable than those fishes that had been injected with dye.

New evidence has proven that Parrots are injected with dye.

However, new evidence has proven that these fish are also being dyed via injections of colourant. The injections are made using a hypodermic needle filled with dye and several injections are made over the course of a day.

The fish initially has a stripe along its flank marking the dye injections, but these eventually spread through the tissue to produce a more solid base colour.

What types of fish are being dyed?

At the moment, the practise is only being applied to tropical freshwater fish, mainly transparent species and albinos, since the dye shows up better on them. There are too many species sold in the industry to list each form by name. We would advise shops to excercise caution when ordering from Singapore, Malaysia or Thailand suppliers and to avoid anything labelled "coloured", "color", "art" or "painted". Avoid anything that is available in several colour varieties, especially if those include atypical colours, such as green, blue or purple. A list of the dyed species offered from one Thailand supplier can be seen in Dr Peter Burgess and Dr Stan MacMahon's original article on dyed fish.

Is this illegal?

No. The sale of dyed fish is currently not illegal in the UK. Defra and the RSPCA confirmed to Matt Clarke that the dyeing of fish may constitute mutilation and would be illegal if it were done in the UK. However, the existing legislation allows mutilated animals to be sold here.

Many experts had believed that the forthcoming Animal Welfare Bill would make the trade illegal. In February 2006, we exposed a loophole which means that the trade is likely to continue under the new legislation, because the mutilation occurs in another country.

OATA is unable to ban the sale of such fish, but recommends that its members do not stock dyed fish.

What are Kalideoscope gouramis?

These fish are the white form of the Giant goramy, Osphronemus goramy, and made their first appearance at the Aquarama trade shown in 2004. They are hand-coloured at over 30 sites on each flank. We believe that they are individually tatooed. Others (including those who sell them in the shops) claim that they are hand painted, or even genetically modified.

The gouramis have recently appeared on sale in Essex. Don't buy them! Besides being a cruel and unneccessary process, the species can reach over 60cm/24" in length. At other locations similarly marked fish have been on sale with words marked on their flanks. Clearly words cannot be written on the flanks of fish using genetic modification, making this suggestion preposterous.

What evidence do you have on this?

Back in 1998, Practical Fishkeeping experts Dr Peter Burgess and Dr Stan MacMahon published the results of their research into this in the magazine. They purchased Painted glassfish, or Disco fish as they are also known, and sedated them with a special anaesthetic so they could be viewed under a microscope.

Burgess and MacMahon found that the dye in these fish is not on the surface of the fish, but actually under the epidermis. The dye also moved when light pressure was applied to the coloured area.

In order to achieve the pattern seen in the dyed fish, the dye must have been injected into the fish at numerous different sites on the body. Their fears were proven a few years later when photographs were obtained showing a worker injecting the dye into glassfish using a hypodermic needle and syringe.

How harmful is this to the fish?

If you look at the size of the fish and the bore of the needle used, and make a comparison of scale, it would be the equivalent of us receiving several injections with a needle the same diameter as a pencil.

Burgess and MacMahon say that it is unwise to inject fish of this size anyway, and can understand why the alleged number of mortalities caused by the dyeing process is so high.

New research has shown that fish are capable of feeling pain, so this is likely to be a very stressful process for the fish.

Is there an increased disease risk?

Burgess and MacMahon's study of Dyed glassfish found that 40% of them were suffering from Lymphocystis virus, a disease which causes crusty white growths to appear on the skin and fins. By comparison, less than 10% of the wild glassfish they studied had Lymphocystis.

Where can I find more information?

We have archived the original article by Dr Peter Burgess and Dr Stan MacMahon on the Practical Fishkeeping site.

What should I do if I see them for sale?

First, don't buy them! By purchasing these fish you'll be sending a message to the dealer, and his supplier, that these fish have a viable market among the fishkeeping community.

Politely speak to the dealer and ask him if he is aware how the fish came to get their unnatural colouration. Some may not realise that fish are dyed, others may have genuinely been sent the fish without actually ordering them. Substitutes are quite regularly sent by suppliers if stocks run low on the species the dealer has ordered, so don't take it out on him. It may not be his fault.

Let him know how they are dyed, and point him in the direction of our website so he can read up on the subject. You could even print out his page and take it in to him.

What is your campaign about?

Back in 1996, when these fish were starting to be more widely seen in the UK's aquatic shops, we launched a successful campaign which asked shops to sign a pledge saying that they would not stock them.

That campaign led to a massive reduction in the number of dyed fish sold in the UK, and raised awareness of the processes among fishkeepers and the trade.

Over the past couple of years, we've suddenly seen an increase in the number of dyed fish on sale. So we've relaunched the campaign and this time we're going global.

Who can sign up?

The campaign is open to any shop, wholesaler, freight forwarder or fish farm who deals in live fish anywhere in the world. It is not just restricted to the UK.

If you would like to help the fishkeeping hobby stop this cruel trade read how you can help.

Further reading

Clarke, Matt (2006) - Pink danios: dyed or genetically modified?, Practical Fishkeeping blog. Mon June 19, 2006.

Clarke, Matt (2006) - Magazine publishes guide to cosmetic fish surgery, Practical Fishkeeping website news. Mon June 12, 2006.

Clarke, Matt (2006) - Time to email your MP?, Practical Fishkeeping blog. Thu March 16, 2006.

Clarke, Matt (2006) - It wouldn't happen to a kitten, Practical Fishkeeping blog. Wed February 22, 2006.

Clarke, Matt (2006) - Company offers custom fish tattoos with laser, Practical Fishkeeping website news. Thu February 23, 2006.

Clarke, Matt (2006) - Dyed fish to remain legal, Practical Fishkeeping website news. Fri February 17, 2006.

Clarke, Matt (2005) - New dyed tropical fish on sale, Practical Fishkeeping website news. Thu December 15, 2005.

Clarke, Matt (2005) - Are dyed fish here to stay?, Practical Fishkeeping blog. Mon October 24, 2005.

Clarke, Matt (2005) - Fashions in fish sales, Pet Product Marketing/Practical Fishkeeping website. January 18, 2005.

Clarke, Matt (2005) - Dyed fish campaign hits halfway mark, Practical Fishkeeping website news. Fri July 22, 2005.

Clarke, Matt (2004) - Join the global fight against dyed fish, Practical Fishkeeping website news. Fri December 17, 2004.

Clarke, Matt (2004) - Practical Fishkeeping relaunches Dyed Fish Campaign, Practical Fishkeeping website news. January 23, 2004.

Burgess, Peter and Stan MacMahon (1998) - Why it's cruel to dye, Practical Fishkeeping magazine. March 1998.