Sobo Aquarium Internal Filter FK-1502 Filtration is the heart of an aquarium. Fish needs to be crystal clear water to stay in an aquarium healthy. Filtration can be biological, mechanical and chemical. Sobo Internal Filter FK-1502 is a mechanical filter. It’s sponge absorbs dirt and clears the water. This is Suitable for both fresh and salt water. It is Fully submersible and ideal for any aquarium filtration. This is Super quite, efficient energy economizing and easy to clean.