Hanna Pocket Checker for Phosphorus (ULR)Hanna Pocket Checker for Phosphorus (ULR) (not suitable for cold water aquariums) Specially designed for salt water aquaria, the Hanna Pocket Checker for Phosphorus (ULR) will measure vital phosphorus levels even at exceptionally low range. Phosphorous (as phosphate) is introduced to aquaria through feed, decaying plant and animal waste and even tap water. However phosphate is a driving factor in excess algae growth and without adequate checks, the