Injecting dyes causes damage - who'd have thought it?


It should come as little surprise to find that injected fish apparently suffer with health problems on a muscular level. In a short communication, Serafin Gomez of the University of Murcia (Spain) reports on damage caused by injecting fish with dyes.


The results indicated in the communication come as little surprise to us here, and likely will not surprise anyone who has come across dyed fish themselves. There is ample anecdotal evidence of tumour-ravaged fish, especially dyed Glassfish, but also much feedback on fish such as Corydoras which become infected through their injection wounds.

Gomez writes: "Relationships between painting and induction of diseases within the glassfish are poorly known, although it is hypothesized that artificial pigmentation may cause lesions in this species."

What is significant is how little formal research has taken place into the correlations between dye use in fish and potential for illness, which is why articles such as Gomez’s have high value for those within our industry. In his communication he reports: "In this case, granulomas were investigated in the tissues of an artificially stained glassfish in an aquarium fish shop."

We do have some information on Green terrors (Aequidens rivulatus), and Gomez writes: "it is known that the procedure of artificial stain by injection increases mortality because of handling and chemical embolism."

So, what was found? Well, Gomez notes: "Histopathological examination of the lesion area revealed a typical granulomatous arrangement of inflammatory cells surrounding a foreign pigmented material "

To put that into bite sized chunks, by using a microscope and slices of tissue from the affected regions, Gomez found collections of immune response cells containing dyes, with the suggestion (my own, not that of Gomez) that the granulomas were there as a direct result of the dye.

Gomez later states that "The histopathological findings observed in this case demonstrate that granulomatous dermatitis and myositis as a pathological reaction to the artificial pigment induced a granulomatous foreign body reaction."

To make that a bit easier to digest, if you read 'granulomatous dermatitis' as inflammation of the skin, and 'myositis' to read inflammation of skeletal muscles (usually caused by injury, infection or auto immune diseases) then it should make a bit more sense. In a nutshell, what is being said is that injecting the fish with dyes causes an inflamed reaction, followed by an attempt by the body's own immune system to contain the foreign substance, which in turn causes more damage.

Taking the righteous pulpit, I could sum up a lot of this important work by saying what many of us knew all along – injecting fish with dyes doesn’t do them any good at all. I am, however, incredibly grateful to those like Gomez who are giving us the information we need to finally put this unsavoury aspect of the trade to bed once and for all.

PFK has championed the cause of removing dyed fish from the industry for many years, starting back in 1996, followed by a resurgent, worldwide push of the Dyed Fish Campaign from 2006 onwards.

For anyone interested in reading the full paper, entitled Histological lesions induced by exogenous pigment in dyed Indian glassfish, Pseudambassis ranga (Hamilton), then you’ll need to acquire a copy of the Journal of Fish Diseases.