Our BH-100 is our entry level HOB skimmer design. The pump is 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 pump in place as the instructions list and it is ready to skim. The Reef Octopusskimmers 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 BH100 skimmers as of June 1. Below are the test results from the old impeller to the new improved impeller.