MS-222 is a commonly utilized product for stunning fish if your implanting radio tags or doing electroshock surveys, its the industry standard. The half life is really short, (drug wears off fast) halving the quantities in the body in about 1 1/2 hours. Typically MS-222 should be UNDETECTABLE in a fish after 24 hours. I see this as more of a cover your butts scenario than any potential health risk. Although, MS-222 does test positive for cocaine.