- Adjustable hose length: the hose can be manually cut to set the desired refill depth for your aquarium. - Compatibility and fittings: designed for aquarium walls with thickness 5 mm, 6 mm, or 8 mm. Includes an international standard cola bottle and a thread compatible with standard domestic Coke bottles. - Refill bottle included: comes with its own water refill bottle for convenient top‑ups. - How it works: uses a differential pressure pipe. The water contact end has an oblique mouth. Cut the differential pipe to create a long piece and a short piece; the short piece becomes the water pipe. When the short tube is completely at the liquid surface, refilling stops automatically. - Configurations for different tank walls: two options are provided to fit 5 mm and 6 mm wall thicknesses. - Practical use scenarios: - Automatic top-off for freshwater aquariums to compensate for evaporation. - During water changes, refilling from the refill bottle without manual handling of large amounts of water. - Suitable for tanks with 5 mm, 6 mm, or 8 mm wall thickness, allowing flexible setup across different tank designs.