A competitive enzyme immunoassay for screening and quantitative analysis of malachite green, leucomalachite green, crystal violet and leucocrystal violet in fish and shrimp. Malachite green (MG) and crystal violet (CV) are organic dyes used in the aquaculture industry as fungicides. Due to their toxic effects, they are not authorised to be used in fish for human consumption. The EuroProxima Malachite Green Total ELISA is a competitive enzyme immunoassay for the quantitative analysis of MG, CV and their reduced forms in fish and shrimp.