Most aquarium draining equipment uses a syphon to get the water flowing. The syphon tube is clear plastic, and sometimes it has a much larger diameter tube on the intake end. Just fill the entire thing with water, put the intake end in the aquarium while holding a finger over the output end, put the output end in a bucket, and release your finger from the end. This creates a syphon that will lift the water over the aquarium rim so long as the water level in the aquarium is higher than the output end of the syphon hose. If you want to avoid carrying buckets of aquarium water, consider buying one of the maintenance systems sold by Python, Lee and others. These systems have a pump that fits on a garden hose or faucet and starts the syphon for you. When you're ready to refill the aquarium, just twist and push on a valve, and the water runs the other way. Make sure the refill water is about the same temperature as the aquarium water, and don't use a garden hose to refill an aquarium.
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