they're quite sensitive when it comes to water conditions. they need PERFECT water.
many discus keepers do twice weekly water changes.
a 55 is sufficiant for Discus, i'm not sure how many though. i've heard varying things on stocking these guys.

to get that perfect water some Discus keepers have peat in their filters. they're NOT hardy when it comes to variations in water parameters and tankmates need to be chosen carefully.

have a look at the link below for more details. i've never attempted Discus, they're too expensive to go wrong with!

As Discus can grow up to 8 inches, they require a minimum tank size of 50 gallons per fish full grown. You could keep a young pair in a 55 gallon tank, but will need to upgrade when they reach full size. They require a temperature of 79-86°F and a pH of 6.1-7.5. The overall coloration of Discus will vary depending on the mood and overall health of the fish. It is now the most popular freshwater aquarium fish. Depending on sub-species, the natural range of the Discus extends from the Amazon to the Rio Negro Regions of South America. The Discus requires an advanced level of care due to its feeding habits and water filtration requirements. It is territorial during spawning, but is, otherwise, a peaceful fish. It is among the schooling group of fish. As Discus become slightly territorial when breeding, it is best to breed an established pair, or maintain a group of young Discus and allow them to pair themselves. Warm, soft, slightly acidic water is required for spawning. The pair will clean a flat surface (usually a broad leaf or the side of the aquarium) prior to spawning. The parents must not be removed from the fry; the fry feed on their parents' mucus. Discus are largely carnivorous and prefer freeze-dried bloodworms and tubifex, pellet food designed for Discus, high-quality flake food, and meaty frozen foods.

discus can be very hard to keep.. try www.ageofaquariums.com they might have more info

Discus are not hardy fish. They are sensitive to water quality and are very prone to HITH. I have seen many breeders without substrate in their discus tanks because it is easier to clean the debris. I would also say that two would be max in a 55g, but they do best in groups of 5 or more. Two cichlids is usually not a good number unless paired, because one will always be bullied. I wouldn't recommend them as a solo species either as they are very skittish, and will probably end up hiding, and feeling stressed quite a bit. A R/O unit is not required unless the tap water you use has undesired parameters (e.g. high nitrates, high ph). Although they are a lot of work to keep up, they are some of the most beautiful fish in the hobby. I would say that if you can keep healthy discus in your aquaria, then you are certainly at the top of your game when it comes to fish keeping! Good luck, I hope this helps.

Discus are not hardy and need very clean water-very precise temps
AND they are expensive
I did not have any luck with them even though I removed all gravel from the tank!

This site has great beginner information!

http://members.…