My existing display tank was a gift and it did not come with a screen. I kept reading how it was an important feature to have to prevent fish from jumping out of the tank. The previous owner never had a screen and after searching for one I realized why. It is a corner tank and outside of an expensive custom one they are not available. After the initial cycle I started with some green chromis to get things going. After about a week while I was at work,, my wife sends me a picture of a fish on the floor. That's when I knew I needed to come up with something quick. I made a temporary screen while I brainstormed on how to make something that looked and fit nicely. I did eventually come up with an idea and made one that can be applied to almost any tank. You can view the process on my build thread. If you don't have a screen, don't wait until you find a fish on the floor. Although I don't like losing any fish, I was just glad it wasn't a high dollar one.