Yay! Ottos are schoolers though so three or more would be better if you want to see them out and about!
When I set up the tank, I put everything together, planted it, filled it with water added the worms then gave them a few hours to hide before re-adding the fish.
The more time alone the worms have the better, ideally I would have given them about a month alone but that was not possible since I already had the fish. However the worms are still visible in the tank, so fingers are crossed that their making a colony, if not they also have a 15 gallon dedicated to themselves with no fish to snack on them, just so I always have some around.