ViaAqua® Acro-Cal™ Calcium Reactor offers a simple and convenient solution for maintaining calcium and alkalinity in your reef tank. After the initial setup, the calcium reactor requires minimal maintenance. A calcium reactor is almost a necessity for tanks heavily stocked with stony coral, where calcium and alkalinity demands are high and will promote coral line algae growth. Acro-Cal™ Calcium Reactor provides a steady of calcium by using CO2 to dissolve media in the reactor and, thus, releasing calcium into your water. The effluent released also acts as a buffer to stabilize kH. Features: # Built-in water pump and bleed valve # Use in-sump or hanging # Easy twist off top # Bubble counter included AC-10 Model with capacity for 10-75 gal. tank UPC# 006903729079 Bubble counter replacement UPC# 006903729345