1" to Dual 1/2" Aquarium Plumbing Manifold 2 (Pre Built) - Adaptive Reef
1" to Dual 1/2" Manifold designed to be used in bypass or inline.
A reef aquarium manifold is typically a series of valves plumbed into the return line that can be utilized to add additional return runs or to connect equipment that uses aquarium water to function such as a media reactor.
With a manifold you can use your main return pump from a sump style filter to power other equipment in your tank. Manifolds work well when you want to divert water to a reactor or other device in a sump and the water is flowing back into the sump.
The advantage of diverting water from your return pump to run other equipment is you have fewer pumps using power, making noise, producing heat, and requiring maintenance. Because you are diverting some of the return's water flow, it is a good idea to go with a larger or controllable return pump than you usually would.