Painted fish is an ornamental fish that is colored to make it look better. These fish are artificially colored by injecting dye under their skin. This process (also called “juicing”). This processes is achieved by a number of methods, such as injecting the fish with a hypodermic syringe containing bright fluorescent colour dye, dipping the fish into a dye solution, or feeding the fish dyed food.
However, the colouring of the fish is not permanent, and usually fades away in six to nine months.
Methods of Making Painted Fish
There are a number of methods for introducing artificial colour into fish.
1 – Dyes
A common method of creating “painted fish” is through dye injection via syringe. Generally, fish are injected multiple times. Fish may also be dipped in a caustic solution to strip their outer slime coat, then dipped in dye. These methods are reported to have a very high mortality rate.
Many “color-enhancing” foods for ornamental fish are offered to consumers. In general, these foods contain natural dyes, such as beta-carotene, and are not harmful to the fish, although as with other dyeing methods, the effects are temporary. However, one source reports that harmful dyes are sometimes used by wholesalers.
2 – Lasers
Fish can also be tattooed using a low-intensity laser with dye, a process that was developed by scientists for fishing but is now being applied to aquarium fish.
3 – Hormones
Hormone administration can sometimes increase colouration, although it can also render female fish infertile
4 – Genetic modification
Introduction of genes for fluorescent pigments, derived from corals and jellyfish, results in permanent colouration that is also passed on to offspring, without the need to inject or physically modify the fish themselves.
Aquarium fish genetically modified to fluoresce in bright colours under white or ultraviolet light are now available commercially, under the trade name GloFish. The technology was originally developed to produce a fish capable of detecting environmental pollution. These zebrafish and tetras are available in several fluorescent colours, protected by a United States patent.
Painted Fish Varieties
Some species, such as albino corydoras and “painted” glass cleaners, are injected with the dye using a hypodermic needle. More recently (2004-2005), injection-stained albino Plecostomus and Rift lake cichlids have also appeared. Unlike the Indian glass cleaner, most of the dyed fish are albino.
Health hazards to painted fish
A 1998 survey in England found that more than 40% of painted window cleaner fish showed signs of Lymphocystis infection, compared with 10% of unpainted window cleaner fish. Infection can result from fish-to-fish transmission of the virus through infected needles, or from reduced resistance to infection due to the stress of injection. In addition, the fish injected with the dye often died without obvious external symptoms, possibly due to kidney disease caused by the injection.