Eheim
Eheim GmbH & Co. KG is a German company founded by Gunther Eheim, operating in the domain of aquariums and aquarium accessories. It manufactures different kinds of water filters and the associated filter media, pumps, accessories such as aquarium fish feeders, gravel cleaners and garden ponds, while its subsidiaries MP manufacture aquariums and Jäger, aquarium heaters.
Also, a modern and seemingly unrelated domain that Eheim got indirectly involved in is the use of its aquarium pumps in the liquid-cooling systems of overclocked computers. Similarly to aquarium filters, these cooling systems require small water pumps with a low noise level and reliable continuous operation.