I was thinking instead of painting the back of my tank putting car tint but the mirror one so the tank looks deeper and you can see the back of my rock work.... Good or bad???
Bad in my opinion. If you have fish that don't get along with their own type, they will constantly be fighting with the glass. I thought of doing this also but just went with the black background.
As the others said a mirror will b a bad idea imo also. May reflect the light and cuz a glare as well. You can use a black black vinyl paper like I have on my tank instead of painting and if u don't like it u can always take it off