Supplement contains concentrated nickel. 1 ml of the product increases the nickel level by 0.004 mg/l (ppm) in 100 litres (27 US gal) of water. The recommended level of nickel in aquarium water is 0.001 - 0.01 mg/l (ppm). Contains: nickel sulfate hexahydrate. May cause an allergic skin reaction. If medical advice is needed, have product container or label at hand. Keep out of reach of children. Wear protective gloves and protective clothing. Take off contaminated clothing and wash it before reuse. If skin irritation or rash occurs: Get medical advice/attention. Content/container dispose into hazardous waste collection point