I second Beaches. The "fruit" tetra are indeed coloured forms of the Black Skit or Black Widow Tetra, and if memory is serving me correctly they are coloured with dyes, a practice that we do not condone. I would take them back. Aside from this, this species is very nippy with other fish like angels, which you mention you intend to get, and that would be a disaster.
If you are intent on angels, and a 55g is a good tank for them, you should get a group of 5-6. You can read why in our profile, click the shaded name Pterophyllum scalare. It also mentions some suitable and not-suitable tankmates for angels. As Beaches said, when faced with the temptation of angels, many otherwise "peaceful" shoaling fish become nippers. Once has to research carefully.