Easiest Trick for Changing Water

I colored water in a tank to make it easier for you to see it.

Insert one end of the tube into the aquarium.
 Water will fill up the tube up to the level of the water in the aquarium.

 Coil some more of the tube under the water.

 Block the end of the tube with your finger. 

Pull the coiled part of the tube out of water. 

Bring the tube with water in it below the level of water in the aquarium.

 Release the end of the tube.
 The water flows from the aquarium. 

Keep the ends of the tube below water level for continuous water flow. 

Use this technique for changing water in aquariums and never suck the tube! 
Have fun and happy water changing :)