Angelfish do not mix well with discus, discus need small calm peaceful tankmates that allow them the lions share of the food, Think of fish that share the same habbitat like cardinal tetras and rummynoses, some corydoras and fancy plecs as tank mates, dwarf cichlids from the appistogramma family may be ok too in larger tanks. (Discus live in water of 30 to 34 degrees celcius and so have a higher metabolic rate and need more food).
Hill stream loaches are coldwater tropicals, they come from mountain streams and dont tolerate temperatures over 20oC well.
As mentioned the rainbow shark is too aggressive to be kept with discus, the spiney eel may work as they spend large ammounts of time buried in the substrate but will have to be removed if it spooks the discus.