Internal filter for small fish tank 3-18L provides mechanical and biological filtration to help keep the water clear in freshwater and saltwater aquariums. Key Features: 1. Included: • 1x Filter, • 1x Filter Stone, • 1x User Manual 2. Internal filter for a small fish tank provides mechanical and biological filtration to help keep the water clear and the tank healthy 3. Fine sponge catches fish waste and tiny debris while bio balls provide plenty of spacious areas for the colony of beneficial bacteria 4. As an internal fish tank filter, this small filter is a fish-safe seamless design without any moving parts, so it can protect the small fish from getting sucked up 5. Would not suck the tiny fry into the filter and there will not have a heavy load of debris in the water because the biofilter with gentle water flow is great for fragile invertebrates, such as fry fish, betta, guppy, shrimp, and tetras 6. The internal filter is perfect for shrimp tanks, quarantine tanks, or fry tanks 7. Best small internal aquarium filter not only can keep the tank water clean but also agitates water by making bubbles 8. Slowly moves water around which is great for fish that love slow-flowing such as betta and guppy fry fish, etc 9. Replace the sponge with any brand of sponge, just cut to the size and clean the bio balls every two months 10. Replace partial bio balls every six months, and replenish only ⅓ at one time 11. Like most sponge filters, the Hygger small internal filter requires at least a 2w air pump & an airline (both sold separately) to run with 12. A convenient plastic chamber allows for quick and easy access to filter media maintenance or replacement 13. Colour: Black 14. Size: Small 15. Material: ABS Plastic 16. Made in: China 17. Dimensions (HxWxD): 13.7x4.6x4.6 cm 18. Weight...