By no means an expert, but I did extensive research on then earlier this year before deciding they were not for my lifestyle.
The wilds are definetly more sensitive to water conditions, I would stay away from them to start off, and go with a good quality known breeder, as half the time the trouble starts from not getting good stock to begin with. The babies/juvies require excellent water conditions in order to not stunt their growth, its why you hear of people doing daily 90% water changes for young discus, but the more mature adults can handle a bit more, from my understanding a large weekly water change would suffice, you want to keep your nitrates around 10ppm or under, from my understanding of saltwater its 5ppm? so I dont think its as bad as salt.
As far as stocking, 1 per 10 gallons seems to be the rule, and ofcourse over filtration of the tank also helps, you want your water temp as high as possible, most of the expert discus keepers I know keep it around 88, you can keep it lower, but it slows the metabolism, again stunting growth, good tank mates include cardinals and rams, cardinals are shown to actually help the high nervousness of discus and get them to come out and show themselves more.
Dark colors on a discus is bad, it means they are not happy and you need to look into your water parameters or stress, if you need any more information, just pm me and I can direct you towards some excellent discus breeders and information sites where discus is a huge passion!
Forgot to add, discus do like soft water, so depending on your water quality you may need some buffers, I believe ideal conditions are around PH 6.5, GH5, KH3, RO water is unecessay unless your water quality is bad out of the tap, here in BC our water tests out at KH0, GH0, PH 6.8 so I have to buffer mine up to avoid a PH crash, whats your water like in your neck of the woods?
