No you don't have to wet it everyday. Just once. The tricky part is wetting the whole thing and squeezing out the air bubbles (I use a credit card) without soaking the floor. And if you're a perfectionist like me it's a pain to get all the bubbles out. But after you do it initially you don't have to do it again.
I think the water just makes and air tight seal. And that allows the background to be seen really clearly through just the glass and water as opposed to the water glass and air between the background. I think anyway
Good luck. hope it works out for you
