Calcium Reactor 818 All cell cast acrylic construction Clear lid to view proper O-ring seal Key hole slot for lid removal Micro ball valve effluent control Pan World external pump, bolted to base plate pH probe port in lid pH probe adapter included Auto fill bubble counter 13 x 13 foot print, 24" overall height Holds 24 pounds of media, we recommend large grain schuran type Well suited for Large SPS reef displays or commercial holding systems