I currently only have 3 black neon tetras that I bought from petsmart (they only 3 left). They've been in my newly cycled 20 gallon tank for the last 2 days. Even though they are doing fine right now (stopped hiding and are eating flakes), I've heard people say that not having at least 6 of them together will stress them out and cause illness. I'm planning to buy 5 more but the earliest I can do that is next week. Is this going to be an issue where my tetras are temporarily not in a complete school? These are the only fish in the tank.