The Discus or Discus Fish originates from slow moving, soft, acidic waters of wood and leaves in the Amazon basin.  They are sometimes called the King of Aquarium fish.  They require very clean water, so they aren't recommended as a beginner fish.  There are two main species: 

 The Discus has dorsal and anal fins that run together into the caudal fin accentuating their thin circular profile.  The originating wild versions have dark horizontal banding.  There are usually two predominant colors in intricate woven patterns.  Discus have been bred in captivity to produce a wide variation in brilliant colors with names such as cobalt blue, turquoise, red dragon, pigeon blood, royal, marlboro red, snakeskin, ocean green, red-turquoise and blue diamond.  Some show varieties command exorbitant prices.  

Discus grow very large, so a minimum tank size is 40 gallons, which would keep about 4 Discus.  Discus are cichlids and are aggressive, so the best combinations are a single discus, a mated pair, or a large group to spread aggression among.   Although Discus do better in schools, but this is not practical for most aquariums.  The tank should be heavily planted.  Water can be softened by filtering through peat.  Water lilies and floating plant cover provide subdued lighting, which is preferred.  Carbon filtration can help maintain water quality and weekly water changes are a continuous requirement.  Discus will eat Tetra Min flakes, Tetra ColorBits, Tetra Prima, spirulina flakes, spinach, freeze dried bloodworms, brine shrimp, discus pellets, small fish and beef heart.  Feeding Discus can be expensive and also requires clean up to maintain water quality.  Discus are subject to intestinal parasites.  Higher temperatures are suggested for sick fish.

It is difficult to tell the difference between sexes.  The best method of determining sex is to obtain a group of young fish and watch as pairs form.  Spawning occurs on smooth flat surfaces such as leaves, pots, rocks or aquarium glass.  The pair will clean the surface meticulously .  The female can lay hundreds of eggs, which are fertilized by the male after the eggs are all laid.  The parents guard the eggs.  Fry will hatch in about 2 days.  The parents should remain with the fry.  The fry feed on skin secretions from the parents for the first 10 days, after which the parents can be removed and the fry can be fed brine shrimp.

Discus are sometimes considered the ultimate challenge for the freshwater aquarium keepers. Some rumors are true as others are not that accurate. They are surely one of the loveliest fish out there and sometimes very irresistible to buy. So here I put some things I have learned and experienced with some advice.

They are Cichlids from the Amazon River. Even though they are peaceful, they are carnivorous. So proper diet is required as flakes won’t be enough. Experts and breeders recommend feeding them with beef heart. You can actually buy it and prepare a paste to store for some time. They cut the beef heart in small chunks and put it in a shaker with some carrots (for natural color), vitamins and even medication if needed. Make a paste and feed them. But leftovers will decompose in the tank, so filtration won’t be even close to be enough. Water changes will be imperative. But for general people like us, you can feed them with blood worms, frozen foods, and high quality pellets. When they become healthy they will feed even on flakes, but I give them high quality ones like once a week. They prefer eating the food after it is on the bottom of the tank. That’s why it’s recommended to have them with tank mates that aren’t very active eaters. So it’s preferred to have them with small tetras and allow the Discus to be the big fish in the tank.

Water quality is needed, especially if you feed them with meat. But more than that, they need water changes in order to grow. They are very susceptible when young, so you want to help them grow quickly. What’s the key, water changes, water changes, water changes. Many people worry a lot with having them in soft acidic water. After long times worrying a lot with these parameters, I heard and experienced that water changes are the most imperative parameter to have them grow quick and healthy. Where I live the water is hard and with a high pH and the only thing I do is adding an anti-chlorine product. I notice the difference in growth. I also heard that breeders in China don't have filters in the tanks!! They do 50% water changes every other day, that’s all!! Of course they don't have regular tanks like us. Keep in mind that water changes affect plants so plan on getting very strong plants.

Discus are VERY nervous fish. They will jump in panic attacks. So it’s imperative for them to feel secure. Drift wood and plants help a lot, as well keeping the tank in a quiet area. Discus tend to become aggressive between them. There’s always a bully. Many people recommend having 5 to 6 Discus in order spread the aggression not always against the weaker one. They don’t eat each other, but won’t allow the weaker ones to eat. The harassment alone can kill a Discus, as most of them die just because of stress. They become very dark and refuse to eat for days. At that point there’s little you can do. Be aware of this at the moment to buy one. If it’s healthy and he’s dark, in a corner DON’T BUY IT. Ask them always to feed them and watch him eat.

Tank mates: Ideally small tetras, like Neons, Zebras, Rummy Nose. Unless the Discus is 5 or 6 inches (15.24 centimeters), then Neons will be food instead of tank mates. Serpae are nice too.

I’m very experimental and have my Discus with strange fish. I won’t say it will work with everyone but here are the fish I have had without major problems. All types of Neons, Guppies and Platy Hi Fin, German Ram and Gold Veil, Rainbows, Congo and Emperor Tetra, Colidora, Killifish, Betta CrownTail, Rainbow Shark and Chinese Hi Fin (Banded Shark), Plecos and Ottos, and with an Angel.

In general Discus are not easy fish. Even experience people have episodes of them dying for no reason. This delicate fish requires patience, attention and dedication. Also require money spending. I strongly recommend spending exaggerated time watching the fish before buying it. Also try to buy the bigger ones (more expensive at the moment, but keep buying small ones and have them die). So be positive and go for it. Having them is just amazing. Hope this help a bit.