Determination of the phosphate value for optimum plant growth or possible cause of algae in fresh/sea water and ponds. Laboratory comparator system to compensate for inherent water colouration: Fill glass cuvettes with sample water, add reagents to a cuvette, place cuvettes in holder, read off values on colour chart. Application: For new freshwater and marine water: once a week. For algae problems and for tap water control. You can find detailed information on water analyses and problem solutions on the JBL homepage in the aquarium or pond section.