Our BH-300 is a dual pump model that follows the same design pattern as the BH-100 but has two pumps. The pumps are mounted externally so it will sit inside the aquarium. This is a simple user friendly HOB skimmer designed to skim up to a 50 gallon aquarium. Simply place the skimmer on the back of the aquarium, mount the pumps in place as the instructions list and it is ready to skim. The Reef Octopus skimers are powered by the Hailea OTP pumps. They are built with high quality acrylic. The Octopus skimmers uses metric plumbing parts. The pump has an improved venturi design and pinwheel impeller. We developed a new pinwheel impeller that is being provided on all of the BH300 skimmers as of June 1. Below are the test results from the old impeller to the new improved impeller.