I bought 5 Neon tetras about 3 days ago, and they were all shy at first hiding behind the driftwood, but now they are all swimming around except one... There is one neon that just floats around aimlessly in the same spot for minutes at a time then moves a little and floats around some more. It usually does this closer to the top half of the tank, but I have seen it do it other places as well. The rest of the Neon tetras all swim around together usually and they seem to be fine, but this one isolates itself from the others and just floats around. Whenever I drop food close to it, it still floats around not going after the food . There seems to be no discoloration or having any problems swimming. It had schooled up with the rest of the others a few times, but other times just seems to prefer being alone. Any advice to this topic is appreciated!