Hi, I am by no means an "expert" on Discus. I have "one" yes you read right I have just one. I use to breed Angels on a large scale but do not consider myself an expert. I have found with these types of fish if you have a true breeding pair then two is alright, if you do not have a true pair with 2 or 3 you are asking for trouble. Been there and done that.
I would suggest that you get 5 young Discus, let them pair up if they do and then you might have to get rid of the rest. They also may live in harmony too, hard to tell.
Discus require very very clean water. More so when they are young. Many breeders do a 50% water change each and every day. As they get older you can get away with once a week. I do my water changes once a week. I keep my one discus with an Angel, some don't like to mix these two but in my case I lucked out and they are the best of buddies. But...... the Discus is the King of the tank and that shows.
Discus are not readily available here and are very expensive for me to have them brought in. So I just have the one and quite happy with it. It is not spooky since I added the Angel and is a nice size now.
Bottom feeders, cory cats and Bristlenose are the best. The regular Plecos will suck onto these fish and I had to return my young one because of that and bought a bristlenose instead.
As for other fish, I recommend some schooling tetras: rummynose, cardinals, neons if they are not to small, etc.
Keep any fast moving aggressive fish out of the tank.
I also do not adjust my ph, I have high ph and bred my angels just fine with it. When I tried to lower it I killed more fish that it was worth. Discus and Angels will adjust to your wate just fine. But if you are wanting to do the breeding end of things you might have to lower it for that. But if you just want to enjoy these beautiful fish I would suggest to just leave your water alone. I am not a big fan of any additives to my tanks, they all do just great.
Hope this helps, this is what works for me but might not work for others. They are truly beautiful fish that require attention to be paid to their water quality.
bugsy....