Depends on the size of the pup. In smaller tanks like that, you hear about die-offs and other such troubles much more often. The ammonia produced by these little suckers can be startling to someone not used to keeping them. Upgrade as soon as you can, but you would have give or take a year (depending on diet). That said, discus and aros are great tankmates!
Again, I urge that you get a bigger tank when you can, but if you filter very well and religiously change your water, it could work. Best of luck to you!