Aquarium Heater Full And Fully Dipped Submersed Inside The Fish Tank Water It Is Shock Proof, Although We Advice To Switch Off Before Doing Any Work Inside Your Fish Tank. Do Not Use Outside Of Water. When Fixing Inside Your Tank Please See That The Bottom Tip Of The Heater Does Not Touch The Bottom Sand, Or Aquarium Decorations Like Toys, Plastic Plants. Etc. You Can Fix The Heater Inside Water Of Your Tank In Horizontal, Vertical, Or Slanting Position.For Cleaning And Maintenance Work In Your Tank, Remove The Heater After Switching It Off 5Miniutes. The Running Heater Will Get Cool Down By This Time, You Can Gently Unfix It And Remove It And Place It Carefully On Dry Piece Of Cloth. If The Heater By Chance Gets Cracked Or Broken At Some Places, Please Do Not Use It Anymore, Its Not Reparable And Do Not Attempt To Use It.