While they can be difficult for inexperienced aquarium hobbyists to raise successfully, discus fish are among the most popular species in the aquarium hobby industry. One of the reasons these fish can be difficult to raise successfully is their sensitivity to inconsistent water parameters.
These fish are native to the Amazon River Basin, where the water temperature rarely fluctuates more than a half degree at any point throughout the year. As a result, a consistent temperature is necessary in the home aquarium for these fish to thrive. In addition to maintaining a stable water temperature, discus fish also have certain preferences for tank size and water chemistry, as well as tank décor and tank mates.
Quick Summary About Discus Tanks
- Tank Size: minimum 50 gallons, 10 gallons per additional discus
- Tank Shape: tall
- Temperature: 80° to 86° Fahrenheit, recommended 82°
- pH: acidic, 6.0 to 6.5
- Water Hardness: 0° to 8° DH
- Lighting: subdued, full-spectrum, 10-12 hours per day
- Heater: submersible aquarium heater
- Aquarium Decor: live plants, rocks, and driftwood
- Live Plants: Amazon swords, Anubis, Java fern
Preferred Tank Size
Because discus fish grow to an average size between 20 and 25 centimeters, they require a large, preferably tall, tank. A minimum tank capacity of 50 gallons is recommended for a single fish. Discus fish are schooling fish, so it is best to keep them no fewer than three at a time. To determine what size tank is needed, start with a base of 50 gallons and add an additional 10 gallons for each additional discus fish. Like all fish, discus fish need adequate space to swim and grow. If the tank is too small or becomes overcrowded, discus fish are likely to become stressed and may end up falling ill.
Potential tank mates should also be considered when determining the proper size for a discus tank. While an 80-gallon tank may be adequate for four discus fish, adding tank mates like tetras may necessitate a switch to a larger tank. The general rule for community fish is to allow one gallon of tank capacity per inch of fish. A 100-gallon tank that houses four discus fish (50 gallons for the first discus and 3 x 10 gallons for the additional ones) could safely accommodate twenty inches of additional stock.
Top Hint: When making these calculations, use the adult size of fish rather than their size upon purchase to avoid future overcrowding.
Discus fish are notoriously sensitive to changes in water chemistry, one of the qualities that makes them somewhat difficult to keep in the home aquarium. The Amazon River, the native environment of discus fish, receives an almost constant flow of freshwater due to the amount of rain the Amazon region receives each year. As such, discus fish require extremely high water quality, which can only be achieved through frequent water changes and adequate filtration.
In addition to receiving a consistent influx of fresh water, the Amazon River maintains a fairly stable temperature of around 80° Fahrenheit. In the home aquarium, it has been found that discus fish are better equipped to resist disease at higher water temperatures between 80° and 86° Fahrenheit. Temperatures this high can lead to increased algae growth. However, so many aquarists recommend a tank temperature of around 82° Fahrenheit. Oxygenation is another concern at higher water temperatures. Cultivating live plants in a discus tank can help counteract warm water’s lower oxygen capacity.
Manipulating Water pH
The Amazon River generally maintains a pH between 4.0 and 7.0, though most discus fish prefer acidic water with a pH in the 6.0 to 6.5 range. PH can be controlled through the addition of commercial compounds in non-planted tanks but, in planted tanks, these methods may lead to excessive algae growth.
Adding sodium bicarbonate (NaHCO3) to tank water increases KH or alkalinity and injects carbon dioxide (CO2) to buffer it is a traditional method. In addition to these methods, there are several ways to increase or buffer the pH in a discus tank naturally. Inserting peat moss into the filter pad or adding black water extract are two simple and natural ways to alter the water chemistry in a discus tank so it more accurately mimics the conditions in the Amazon River.
Water hardness is the final component of water chemistry that must be considered when maintaining a discus tank. Water hardness is generally measured in terms of general hardness (GH) or carbonate hardness (KH), also referred to as alkalinity. The water in the Amazon River is relatively low in mineral content, making it fairly “soft”. Thus, the recommended water hardness for discus tanks is between 0° and 8 °DH, though some species can tolerate a hardness up to 12°.
Filtration, Heating, and Lighting
In their native habitat in the Amazon River Basin, discus fish are used to warm, slow-moving water and low lighting. For discus fish to thrive in captivity, these conditions must be reproduced as closely as possible. To achieve adequate filtration without creating an overly strong current, some discus fishkeepers employ multiple filters. A power filter is recommended for large tanks to provide adequate aeration and facilitate mechanical and chemical filtration. Sponge filters make excellent supplemental filters for discus tanks because they provide biological filtration and help control solid waste and debris build-up. When selecting a filter for a discus tank, keep the tank size in mind and select a filter with a low-flow output setting.
There are several types of aquarium heaters on the market but, among these types, two are most frequently recommended for discus tanks. A submersible aquarium heater can be completely submerged in the tank. This type of heater should be placed horizontally along the tank’s back wall near the bottom. This position will allow for the evenest distribution of heat. Hang-on aquarium heaters are those which can be inserted vertically into the aquarium and suspended through the use of suction cups or a plastic or metal hanging device. These heaters are somewhat less efficient than submersible heaters because the heat distribution is concentrated around the tank area where the heater is hung.
Because aquarium heaters come in various sizes, selecting the size best suited to the tank capacity is imperative. For particularly large tanks, it may be wise to implement two smaller aquarium heaters than a single large one. This will not only ensure the even distribution of heat but also, should one of the heaters fail, the resulting drop in tank temperature will be less sudden.
When browsing the selection of aquarium heaters, look for a model with an external control option. This option allows the hobbyist to monitor the device to be sure it is functioning properly. Utilizing an in-tank thermometer is another simple way to monitor tank temperature and the function of tank heaters.
The water in the Amazon River contains tannins, a substance that reduces sunlight and makes the water appear murky. To mimic this condition in a home discus tank, it is necessary to provide subdued lighting. There are a variety of options when it comes to aquarium lighting, but not all types are recommended for discus tanks.
Florescent lighting is the cheapest option and uses the least energy. An aquarium hood is the most common way to utilize this type of lighting. Compact florescent lighting is more powerful than regular florescent lighting even though the bulbs are typically smaller. T-5 high output fluorescent lights are very compact and powerful but put out intense light that is not recommended for discus fish tanks.
Metal halide lights are recommended for large or deep aquariums like discus tanks but they can be quite expensive and should be used with caution because they have a high heat output. When using metal halide lights it is wise to set up auxiliary fans to keep the lights from heating the tank. Light Emitting Diode (LED) lights are becoming increasingly popular because they provide the same power as metal halide lights without the hazardous heat. Regardless of the type of bulb, lighting in a discus tank should be full-spectrum to enhance the appearance of discus fish and to enhance live plant growth. Leave aquarium lighting on for 10 to 12 hours per day in a discus tank and always turn it off at night. If the lighting is too bright, discus may hide and may not come out until the light is turned off or the intensity is reduced.
Plants and Aquarium Décor
Discus fish are a peaceful but often shy species so they prefer a tank that offers a variety of hiding places. In their natural habitat, these fish can hide among aquatic plants and submerged tree roots, using their natural coloration as a means of camouflage. Incorporating live aquarium plants into your home tank is a great way to enhance its aesthetic appeal while providing a more natural environment for your fish. Live plants also help to oxygenate tank water, control algae growth and may harbor colonies of beneficial bacteria essential to the proper maintenance of the nitrogen cycle. However, keeping discus fish in a planted tank is somewhat more difficult than maintaining a planted tank with other species of fish.
Live aquarium plants require nutrients and a ready supply of carbon dioxide (CO2) to thrive. In a regular fish tank, plants garner nutrients from the uneaten fish food and organic waste that accumulates along the bottom of the tank. Since discus fish are so sensitive to poor water chemistry, it is necessary to perform frequent water changes and vacuum the gravel to keep water quality high. Performing these tasks can not only become a hassle in a heavily planted tank but it can also reduce the number of nutrients available for live plants.
In addition to the problems associated with frequent water changes, the water temperature most discus fish prefer is somewhat higher than that at which live plants are likely to thrive. To keep live plants in a discus tank, the hobbyist should select varieties that are tolerant of warmer water temperatures. Some plants recommended for discus tanks include those native to the Amazon region like the Echinodorus family, which includes Amazon swords. Anubias, though native to Africa, are hearty plants that tolerate low light and mix well with swords. Java fern and plants belonging to the Micranthemum and Hydrocotyle families also do well in a discus tank. North American species such as Amoracia aquatica, Bacopa caroliniana, and the Samolus parviflorus are adapted to cooler waters and should not be kept in a discus tank.
Because discus fish are so big, large rocks and pieces of decorative driftwood are generally not recommended for discus tanks. These decorations may end up being obstacles for discus rather than helpful hiding places and they may also put discus fish at risk for injuring themselves. The ideal decorations for a discus fish tank include broad-leafed plants, small rocks and floating plants. Driftwood may be used in a discus tank if it is laid horizontally along the bottom of the tank instead of standing upright where discus fish may run into it.
Though hiding places are essential to the well-being of discus fish it is also necessary to provide plenty of open space for swimming. When decorating a discus tank, it is wise to concentrate taller plants near the back of the tank, layering shorter plants toward the front. This arrangement will allow discus fish to hide in the tall plants at the back of the tank when they choose while leaving most of the space near the front of the tank open for swimming. Place tall or upright tank decorations in the corners or lean them against tank walls so they do not become obstacles that discus fish may encounter.
Because discus fish have such specific requirements for water quality it is wise to design your tank around the needs of your discus fish. Once you have met the needs of your discus fish you can begin to think about adding other fish which can fit into the existing tank parameters – do not try to add discus fish to an already established community tank because the water quality may not be sufficiently high to keep your discus fish healthy. Remember that discus fish are schooling fish and should be kept with others of their own species and any other tank mates you hope to keep.
If you ask around many hobbyists will say that Discus Fish should be kept on their own. I.E. they should not have any tank mates as they don’t compete well with more aggressive eaters that will get to the food before the Discus are even aware that it is in the tank. However, you can still achieve some tank mates with some careful planning.
When selecting tank mates for your discus fish, you would do well to remember that discus fish are peaceful and non-aggressive. This being the case, it is wise to pair discus fish with other community fish, particularly schooling varieties. Discus fish can be tentative in the home aquarium but if they see other schooling fish out in the open they may feel more comfortable and be less likely to hide among the plants in your tank. Many hobbyists have had success keeping their discus fish with some of the smaller species of gourami such as pearl gouramis, but blue and gold gouramis are too large and too aggressive to be kept with discus fish.
Some of the best tank mates for discus fish are characins. Characins are a family of freshwater tropical fish which includes tetras. Because many of the species belonging to this family are also native to the Amazon regions of Central and South America, they are a good fit for a discus fish tank. Additionally, tetras are generally small, peaceful fish that will not likely bully your discus fish. Popular species of tetra that can be kept with discus fish include neon tetras, glowlight tetras, bleeding heart tetras, and rummy nose tetras.
In addition to tetras, a variety of bottom feeders can be kept safely in a tank with discus fish. These work well because they will pick up the food that the discus fish miss. Corydoras catfish, or cories, remain relatively small and make excellent community fish. Also a schooling variety, cories will make your discus fish feel more comfortable while helping to control the build-up of detritus at the bottom of your tank.
Other bottom feeders like small plecostomus, Siamese algae eaters, loaches and ottocinclus should also be considered. If you keep ottocinclus or plecostomus, be sure to provide plenty of algae wafers or spirulina discs to prevent these fish from being tempted to feed on the mucus layer that grows naturally on the skin of your discus fish.
Recommended Tank Mates
- Other Discus Fish
- Tetras (Cardinals, Glowlight, Neon or Rummy nose)
- Catfish (Whiptail or Ancistrus)
- Fancy Goldfish
- Angelfish (Some of my friends have put these together. However, the risk of spreading the disease is increased)
- African Cichlids
- Tiger Barbs
Discus Tank FAQ
How often should I perform water changes in my discus tank?
There is no correct answer to this question because different tanks have different water chemistry, affecting the need for water changes. The best option is to change the water in your discus tank as often as possible. Performing 25% water changes at least once a week is important for keeping the water quality in your discus tank high. More frequent water changes may help reduce the buildup of nitrates in your tank, creating a healthier overall environment for your fish.
How many discus fish can I keep in my tank?
The number of discus fish you can safely keep in your tank depends on the size of the tank. The minimum tank requirement for a single discus fish is 50 gallons. Each additional discus fish should be allocated a minimum of 10 gallons. Thus, a 100-gallon tank can accommodate 6 discus fish.
Can I keep discus fish with other cichlids?
Discus fish should not be kept with aggressive fish or with fish that are larger than the discus fish. African cichlids in particular are known for being aggressive and should generally be kept in a tank alone. This is the case, keeping discus fish in a tank with African cichlids is unwise. Discus fish may be able to get along with smaller, non-aggressive cichlids like dwarf cichlids and rams. Still, it is best to cultivate a discus-only tank or to keep them with bottom-feeding community fish as discussed earlier.