Malachite Green has been extensively used for the treatment of fungal infections in fish by the aquaculture industries in Europe, and throughout the world, for many years (7). A recent review has confirmed concerns regarding the use and toxicity of Malachite Green. The toxicity of the dye increases with exposure time, temperature, and concentration and, has been reported to cause carcinogenesis, mutagenesis, chromosomal fractures, teratogenicity, and respiratory toxicity (8). In fish, Malachite Green is extensively metabolized to the colourless compound Leucomalachite Green, which is stored in fat (9). The elimination rate in fish is dependent on the fat content. Residues of Malachite Green and Leucomalachite Green have been reported in serum, liver, kidney, muscle, eggs, and fry (9). Residue monitoring is reported to be more effective when the sum of Malachite Green and Leucomalachite Green are measured (10). It has been reported that the concentrations of Leucomalachite Green always exceeded those of Malachite Green (11).