Gulfstream Tropical AGU00529 Ista Max Mix Co2 Reactor for Aquarium, Large MOST EFFICIENT: The Max Mix Reactor will dissolve 100% CO2 into the water. Patented impeller design completely eliminates the CO2 bubbles EASY ASSEMBLY: No tools required for setting it up. Diagram set up instructions printed on side of box illustrates exact position of reactor COMPACT: Makes it easy to fit exactly where you need it, internally or externally DURABLE: Resistant to acidity and impact. Easy to clean and simple to maintain Large size is designed for pumps from 250 to 500 GPH