They're very sensitive to water quality, and to copper-based medications. Water in the tank has to be kept very clean. If you're committed to weekly water changes on the tank, and if the tank is not overstocked, I'd say go for it.
They do get larger than 3", though. Allivymar (former advisor here) had one that was pushing 5", and other reports on the net confirm this.
They're quite interesting creatures, and will do their best to get close to the outflow of your filter, where the water flows fastest, and they can pick up the most debris.