Malachite green: its toxicity to aquatic organisms, persistence, and removal with activated carbon

The acute toxicity of malachite green was determined in standardized laboratory tests for chinook salmon, coho salmon, Atlantic salmon, brown trout, rainbow trout, brook trout, channel catfish, largemouth bass, smallmouth bass, bluegill, snails, Asiatic clams, ostracods, freshwater prawns, larval midges, naiads of mayflies, adult newts, larval leopard frogs, and larval toads. The invertebrates exposed were generally more resistant than the fish and amphibians. The toxicity of malachite green to fish was not affected by water hardness or pH (except bluegills), and was increased only slightly by increases in water temperatures. Malachite green was very persistent in aqueous solutions; it did not detoxify after 3 weeks of aging in glass containers. The chemical is readily absorbed from aqueous solutions (pH 7.5, total hardness 44 mg/liter, temperature 12 degrees Centigrade) by filtration through activated carbon; the capacity was 23.4 mg of malachite green per gram of carbon.