When I stocked my tank I asked for 10 ember tetras. After watching for a month this particular fish just doesn’t seem like it’s an ember. I can’t find any other fish that looks like it. The embers are a transparent red and they rarely move their fins when swimming. This fish is more silver and not transparent, with red fins and a black spot on his tail. When he swims he darts forward and stops on a dime and begins vibrating his fins before darting again. Watching them together, he acts completely different than the embers and doesn’t even school with them. Can someone please tell me what kind of fish this is?