I would also advise against housing them together unless you've had years and years of experience, and even then, I'd suggest you re-think it.
When I kept my corn in a tank I gave her nice deep eco-earth, enough to tunnel in. She also loved a deep bed of aspen so either works. Corns sometimes like something to crawl around on, so I gave her a large branch (plastic but heavy) to crawl on, two hides, and of course her water bowl. That's really all they need.