Malachite green was classified as a class II health hazard and showed a significant health risk to human through consumption of fish that contain (MG) residues. In addition, MG was heat stable and thus may not be degraded during routine fish processing. Due to effectiveness of malachite green and relatively low cost, it was a procurable agent for freshwater fish farmers; these compounds might influence the immune and reproductive systems. It was also carcinogenic, mutagenic and teratogenic agent so; sixty fish samples, 20 tilapia fish, 20 mullet, 10 bass and 10 shrimp were randomly collected from various regions at Damietta governorate (Egypt). All samples were evaluated for malachite green (MG) residues.  Mullet samples fish were significantly (P < 0.05) had the highest concentrations of malachite green residues. The mean ± S.D values of malachite green residues levels were as 1.558 ± 0.165ppb in mullet, 1.374 ± 0.326 ppb in tilapia, 0.719 ± 0.148 ppb in bass, as well as 1.213± 0.130 ppb in shrimp, while the minimum values were < 0.3 ppb and the maximum residues levels were as 2.61, 2.76, 1.18, 1.43ppb respectively. Fish samples positive for MG were treated by different heat treatment (microwaving, roasting and boiling). The reduction percentage for malachite green residues were 81.80%, 32.90%, and 100%, consecutively.
Comparing the results of malachite green residues in samples with Commission Regulation (EU, 2004) for maximum residues limits, it was clear that 6 (10%) of examined samples were more than MRLs which was 2 μg/kg.