Imo, a 55 is bare minimum for a shoal of discus (I prefer something bigger tbh). They can get pretty sizeable with good husbandry and can fill out a standard 21" height. But it is doable.
And it's only worth getting if you know you are able to properly take care of them. starting with juvies is cheaper but requires more responsibility in ensuring they grow healthy until adult size when you don't have to be as vigilant with WC. Likewise, starting with adults means "less" husbandry at first, but it is much more expensive
It really boils down to what your schedule is liek and what you can handle Although if you have any questions, feel free to ask away!
I would ask yourself if it is worth the time and money after reading the sticky's in the discus section
Obviously, I do as I have been keeping them almost 15 years- but, a majority of fish-keepers say "No" after seeing how time-consuming their care is and how expensive they are.
Discus are interesting, because they are seen as a sort of Holy Grail fish. They are certainly another level for a beginner to look at, because they demand really organized care. They also demand more space than a 55, in my estimation. others will disagree. I like 20 gallons per adult.
Lots of fish are just as demanding and just as beautiful, but they have never developed the mystique. They are stately and elegant.
I tend to stay away from larger, super delicate fish. With my job, family and health, I prefer fish that let me miss a water change. Discus, Geophagus and fish like them need too much attention, even though they are wonderful fish.
Well I have the time and plan on getting juvies and getting a 100 to 150 gallon tank soon soon I just didn't really know what all they need needed everywhere you read is different.....I want to have some sort of sand and live plants.....does anyone know of any sand that's good for them and plants