Sure you can do this, some people have. Is it a good idea? Probably not, unless you have a really huge tank. Otherwise, they are bound to be stress issues to some degree, and discus may seek cover if they have it for a good portion of each day. The extra stress would no doubt weaken their immune system somewhat , and thus shorten their lifespan over time. It's just like people who smoke. Sure you can do it, but it may shorten you're life in the long run. Discus do best, and grow the largest when they are with their own kind, in a stress free environment.