If someones' Discus just sits there all day, they aren't providing a good home for them. Or, they bought sick Discus...
There's tons of info on these fish that many call --- Kings of Aquariums ---
One website that specializes in them is www.simplydiscus.com
There are a few "loose cannon" fanatics there, so be ready and thick-skinned for severe criticism. Overlooking those types, the info is really good and thorough.
That's not the only good website that has Discus the spotlight, there are many others and lots of good personal websites..