You CAN keep them singly, they just do much better in a shoal. Which is what these guys are saying. They're happier in a group, kinda like you and your buddies.
Right now, as long as you're considering upgrading (and actually DO it!!) you're tank is fine as a grow out tank, he's not going to hit 10 inches overnight, and your starter tank is better than mine was (a 10 gallon). You'll want a 29-30 MINIMUM, but as they always say, your tank can never be TOO BIG! And you'll want to upgrade him as soon as you can.
Right now, as long as you're considering upgrading (and actually DO it!!) you're tank is fine as a grow out tank, he's not going to hit 10 inches overnight, and your starter tank is better than mine was (a 10 gallon). You'll want a 29-30 MINIMUM, but as they always say, your tank can never be TOO BIG! And you'll want to upgrade him as soon as you can.