All Discus fish variants originate from the Amazon region in
Discus cichlids are not very competitive and if you place them in the same aquarium as more assertive , e.g. Angelfish, your Discus might be without food and starve or suffer from malnutrition. More docile species are therefore recommended as tank mates. Keeping several Discus cichlids together is a very good idea since Discus cichlids feel more at ease when in a group. A small group consisting of 6-8 specimens is ideal if your aquarium is large enough. You can also keep Discus with schooling fish, e.g. characins, since their presence will have a calming effect on the Discus. It should however be noted that Discus can consider smaller fish as food if it has not been brought up together with small fish.
The Blue Discus (Symphysodon aequifaciatus haraldi) is also known as and Turquoise Discus. A Blue Discus fish with strong blue lines is called Royal Blue Discus. A Red Royal Blue Discus will have red markings in addition to the blue ones. The Blue Discus variants can reach a size of 15 centimeters (6 inches). The Green Discus (Symphysodon aequifaciatus aequifaciatus) has turquoise and blue markings on its head and upper body. The anal and dorsal fin is also turquoise. The Green Discus will reach the same size as the Blue Discus. The Brown Discus (Symphysodon aequifaciatus axelrodi) will also stay at a size of 15 centimeters (6 inches). Its body is brown or yellowish brown.
The Heckle Discus (Symphysodon discus) is commonly referred to as just “Discus”. It is sometimes also sold as Pompadour Fish. It will grow larger than Blue, Green and Brown Discus and a size of 20 centimeters (8 inches) is not uncommon. The Heckle Discus is also more complicated to keep than the Blue, Green and Brown Discus variants. Even advanced aquarists consider the Heckle Discus to be a challenge, since this discus is very sensitive to changes. Even small changes or tiny amounts of pollutants can weaken the Heckle Discus and make it unable to withstand diseases