Blueface angel are normally quite shy, it should be added 1st. Since you have other established fishes you might need to catch the blueface and house in a corner using and egg crate (Like Brother Earth did, see his post on angels tank)
Or like what i did if space is a problem. Bought those plastic mesh from any DYI shop, rolled it up into a huge tube, secure it with cable tie and housed the angels in there.
I kept my angels for about 1 mth before i let it go also from here you can train it to eat pellets. It works!
Best also to release it at night.
Hope this helps