To appeal to consumers, some ornamental aquarium fish are artificially coloured, They are called Painted fish.
The fish are sedated before they are injected with a bright fluorescent colour dye, so they feel no pain. Alternatively they are dipped into a dye solution, or fed fish dyed food.
This gives the fish a brighter colour and they look more attractive to consumers. The colouring of the fish fades away after six months.
These fishes with single digit tattooed on them are very popular during Chinese New Year. The consumers think that keeping these fish bring prosperity.
Is it necessary to hurt the fishes just for quick monetary gains?
First Commenter - levian