I got a big school of serpae tetra yesterday, bu they were in the same tank as a school of orange mickey mouse platy. Since their color was so similar and they were only a tiny bit bigger than the tetra, I accidentally ended up with one platy in the mix. Do they school? Do I need to get more? Is it ok if I only got 1 or 2 more, or do they need a bigger group like tetras do?