In nature the population of zooxanthelle is controlled by the level of nutrients (nitrates and phosphates) present in the water. In a modern reef aquarium environment control of zooxanthelle, through the reduction of nutrients (nitrates and phosphates), is the best way to get natural colouring of the corals. For this reason it has been a source of study for many years leading to the creation of a multitude of "Management Methods" (Low Nutrients / Ultra Low nutrients).
Whether you are using microbiological methods or methodologies more traditional, when using these systems it is a good rule to keep constantly under control the level of nitrates and phosphates.
ELOS AquaTest Po4-HR is specifically designed to prevent this from happening.
Its precise colorimetric scale allows you to read the level of phosphate in a range between 0 and 0.43 ppm with a minimum reading of only 0.024 ppm of phosphate. Alongside the similar test ELOS Nitrate HR, constitutes the best system for full control of the level of nutrients.