The original GEO reactor is back! This is the design that started the GEO product line and is what the larger models are based on. We put this back into production to offer a high quality no frills reactor at an affordable price. The 418 is suitable for aquariums up to 125 gallons and is built to fit the needs of the average sized reef. Don't be fooled by the small size these are true performers like any of the other reactors in the GEO line up, and just like the other GEO products they are built with the end user in mind.