Zooplankton is a broad collection of small aquatic organisms, in terms of cell number, larger than bacteria, viruses or fungi. These more complex organisms are less susceptible to the effect of oxidative disinfectants than bacteria, but higher concentrations over an extended time period will have a killing effect. This means that raceways treated with (10 - 20 ppm) Halamid should not be released without dilution into surface waters in order to protect natural zooplankton. Stagnant pond systems treated with 1 – 3 ppm with zooplankton present should not show significant negative effect on the proliferation of this zooplankton. This advice has not been lab-tested but is based on practical experience.