Both fish waste and feeding are possible causes for phosphate introduction into the water. A part is taken up as a nutrient by plants, an excess, however, provides nutrition for unwanted algae. The sera PO4-Test quickly and easily provides an overview of current phosphate levels. Excess phosphate is easy to remove with sera phosvec (freshwater) or sera phosvec Granulat (fresh and marine water) or sera pond phosvec (pond). Sufficient for approx. 60 measurements.