OASE Indoor Aquatics Biomaster Thermo 600 External Fish Heater; The OASE Indoor Aquatics BioMaster Thermo 600 External Fish Heater can help to keep your freshwater or marine aquarium at the perfect temperature while maintaining water quality, too. The filter features an integrated heater, so you can minimize the amount of equipment that’s seen in your aquarium. The filter provides four-stage filtration, while sealed pathways mean that water follows the most efficient path through all of the filter media. Water travels through the activated carbon foams which remove toxins and odors, then into the main chamber with filter foams of different densities. You can even customize your pre-filter with different filter foams (sold separately). The filters have an integrated safety locking feature to prevent spills and messy maintenance. You can remove the clean the pre-filter separately from the rest of the filter, which helps to cut down on maintenance and extends the life of your filter. Features like simple priming and adjustable flow control for the inlet and outlet make this a highly versatile addition to your aquarium.