Thanks for all your advice - I wouldn't be completely set on the bleeding heart tetras, I just want to balance the tank with a nice school. I will do some more reading on the ones you mention s mama.
We have a couple angels in a tank with blood tetras and some other fish. If the tetaras are big enouph 2 NOT fit in the angels mouth they would be fine. Make sure you get 6 or more tetras cause they like to be in a group. And little hidding spots incase they get scared. Make sure they have space.