While backgrounds can be permanently siliconed to the aquarium glass, these Mounting Clips allow for installation of some backgrounds on "running" aquariums, essentially eliminating the need to empty and dry the entire tank just to have it intstalled.
When using the Mounting Clips method, we suggest you drain 50-75% of your aquarium (large water change) which will make the installation much easier. Shift as much substrate as you can away from the back glass, making space for your new background. Place the background into the desired position and shift the substrate back against the new background. After placing your background into its final position use the Mounting Clips to secure it on top of the aquarium.
The mounting clips on top, the substrate on the bottom and sheer pressure of the aquarium water will keep the background in its place.