Description Sera Crystal is a biological liquid that coagulates all substances that cause water turbidity, so they are easily removed with the help of a mechanical filter. Ako coagulated particles float on the water surface, remove them using a rake. How to use: Before using Sera Crystal, check the carbonate hardness of the water in the pond with sera-KHTest. If necessary, increase the carbonate hardness, izpolzvlayki Sera GH-KHplus to at least 5 dKH. Too low a level of carbonate hardness affects the stability of the pH value. Then add 50 ml Sera Crystal 1000 l pond water. To increase efficiency, ensure a strong move on the water surface during use. In more persistent cases, repeat the procedure after 24 hours. Keep out of reach of children and pets! Only for ornamental fish not intended for human consumption.