The WAVEREEF Cal-Fit is produced by high-grade cast acrylic pipe plus the heavy PCV parts. Wavereef calcium reactor is computer-precision engineered and utilize the latest aquarium technology to deliver unparalleled performance and value. With a built-in pH probe holder, you can easily keep an eye on the pH inside the calcium reactor with a pH monitor or control the CO2 with a pH controller. A CO2 recovery system re-injects excess/unused CO2. Plus its CO2 reactor chamber, it can mix CO2 better into the water so as to keep your levels balanced, lower CO2 usage and minimize excess CO2 from going back into your aquarium.