This auto water refill device is designed to maintain aquarium water level with your own refill bottle. It uses a standard cola bottle thread and is compatible with domestic Coke bottles. Key benefits - Maintains stable water level by automatic refill as evaporation occurs - Uses your own refill bottle, reducing waste and ensuring safe handling - Compatible with standard cola bottle threads for easy bottle replacement - Adjustable water level via hose length for precise control - Simple, two-position operation for walls of 5 mm or 6 mm thickness Compatibility and specs - Aquarium wall thickness: 5 mm or 6 mm (two operating states) - Includes two tube configurations: long and short; the short tube marks the highest water level line - Thread compatibility: domestic Coke bottle threads; fits international standard cola bottle - Water contact end features an oblique mouth to regulate intake - Hose length is manually cut to set the desired water level Operation overview - When in use, the short tube rests on the water surface at the highest level; water starts to fill - Filling stops when the short tube is fully submerged under the surface - The long tube provides continuous refill capability until the target level is reached What you need - Your own water refill bottle (the product must be paired with it) - A bottle with a compatible Coke bottle thread Material and size - Material details are not specified - Hose length is adjustable by cutting to achieve the desired level use scenarios - Freshwater aquarium top-off: maintain consistent water level and salinity during evaporation - Reef or saltwater setups: prevent excessive salinity drift by automatic top-off - Temporary away-from-home periods: reduce risk of low-water conditions when unattended Notes - The unit has two states for 5 mm and 6 mm wall thickness; follow the corresponding setup for your tank - Ensure the refill bottle is securely threaded and the hose length is adjusted to your preferred water level