Discus and Angels should be ok.
I have a 55 g with 6 large wild caught Discus and 5 wild caught Altums. There's also 3 small clown loaches with them and about two dozen wild caught cardinals. Will be adding another 30 cardinals in a couple of days to replace the ones that disappeared.
Also have another 55g with 6 Abacaxi Heckels, 6 Leopoldi Angels, and a 12 inch Aro. Took out about 50 cardinals that were with them two months ago before I added the Aro.
Also have a 75 g with 6 very large Altums, 2 extra large Zebra Angels, 6 large Heckels from Rio Unini, and two large Clown Loaches about 10 inches each.
I quarantine all new fishes that are introduced to my tanks anywhere from two weeks to six weeks before they get in the mix to minimize health risks to established residents of my tanks.