Lucidum

I currently have a Aneryth Corn Snake hatchling, and I was planning to add another snake to his 20 gallon tank once he gets a bit bigger. Aside from obviously not adding a king snake, are other snakes fairly okay being housed with Corns? I was thinking particularly about housing him with a northern water snake or a garter snake variety, since they have similiar(ish) requirements in temperature and humidity. Eventually the new snake will get its own tank (once the corn's old enough to add another corn for breeding), but for the first year or so, does this seem like it would work?