If they are in new aquariums, they are probably just showing their decor who's boss. They also flare at their reflections, so it's not you. As for the tail biting, it could be boredom or stress.
5 gallon: 1 male VT-Alpha
10 gallon Community: 3 Peppered Cory Catfish, 5 Neon Tetra, 3 ADFs.
3 gallon: 1 male VT-Sub Zero