Brand New Design from CoralVue. Reverse Flow Octopus Calcium Reactors are constructed with high quality Cell Cast Acrylic materials and SCH-80 Hard PVC pipes and JG fittings. Great Value and quality construction. NEW FEATURE: Twist-off top cover for easy service. - Includes pH Probe port for easy integration with pH controller - Equipped with quality circulation pump - Diameter: 140mm (approx. 5.5") - Height: 590mm ( approx. 23 1/4") - Recommended for tanks up to 300 gal.