Ideal Temperature and pH for Discus Fish

By Nadine Oraby | 2020 Update

Discus Fish is notoriously sensitive to drastic pH and temperature changes. Therefore, providing it with a suitable environment is very important.

What is the ideal temperature & pH for Discus Fish? The temperature range that best suits the Discus is 82.0° F – 86.0° F. This is to ensure maximum oxygen content in the water. The pH should range from 6.0 -7.0 as the Discus prefers warm, soft, and acidic water.

To keep your Discus happy and healthy, it is important to know how to maintain stable and consistent water parameters.

Ideal Temperature

Discus requires a higher temperature than most of the other fish species. temperature to be maintained in a Discus’s tank should range from 28°C to 31°C (82°F – 86°F). Wild Heckel Discus, being an exception, prefers water near 90°F.

Coming from the waters of Brazil, Discus genetics are encoded to thrive in a warm environment. If the temperature in your tank drops more than a degree or two below 82°F, or let’s say it remains “cold” for several days, even the healthiest of Discus will become weak and sick. As your fish may become susceptible to stress and parasitic infestations.

Tremendous rise in temperature can also prove to be fatal for your fish. If your aquarium’s temperature goes above 90°F for too long, it might suffocate your Discus as the oxygen level in the water will be dangerously low. You will observe your Discus gasping for air near the surface of the water before it dies or suffers any permanent damage.

Best Water Parameters for Discus!! Talkin Discus Presented by KGTropicals!! (Video)

Regulating discus tank water temperature

In case of overheating, add a few air stones to your tank. This will speed up the cooling process and increase the oxygen level. Make sure you lower your heater’s temperature, too.

To maintain a stable and consistent temperature, you should make use of a reliable and accurate thermometer and heater. Also, you should choose your tank’s place wisely. Do not place it near a window as it might cause a considerable temperature drop. Placing it directly under the sun may as well cause an abnormal rise in temperature.

For Discus fry, high temperature helps to raise metabolism and ensures proper growth. But as the discus fry grow up, the tank should be kept at 82-84°F, otherwise, it will shorten your Discus’s life span by several years.

Ideal pH

A Discus Fish is capable of adapting to various pH levels, provided that it’s not too far from of the ideal range. For a Discus, the ideal range is 6.0-7.0. They thrive in slightly acidic and soft water.

However, they cannot tolerate a constantly changing pH range. It can not only result in weakening of the immune system of the fish but can also cause you the heartache of losing your fish altogether. This makes it clear that stability in pH is very important for a healthy Discus.

Factors affecting pH levels in a tank

Factors that contribute greatly to the pH level of an aquarium are; the trace mineral content, the substrate used, chemical concentration of the water in your tank, use of medication, failure of the filtration system, and certain decorations in your tank such as Driftwood.

Basically, a large drop in pH in a short span of time leads to the shedding of the mucus/slime coat of fish. It is considered as a “partial loss of immune system” because the slime coat acts as a protective layer for them.

As a result, the fish becomes susceptible to fungus and pathogens and can even receive burns to the skin and fins due to the acidity of the water. The Discus fish might as well face respiratory problems which can be easily detected by looking for brown deposits on the fish’s gills, dark coloration or your fish’s attempt to jump out of the aquarium.

High levels of pH can raise the concentration of ammonia which is a toxic compound. This leads to impaired growth, decreased resistance to disease and damages to gills and kidneys of the fish.

Caution in pH adjustment

The pH of an aquarium should be adjusted with great care. Cautious changes of about 0.5 or 1.0 should be made every 24 hours if they are necessary. Some very safe mediums for changing the Ph of your tank include the trace mineral content, the substrate used, chemical concentration of the water in your tank, use of medication, failure of the filtration system and certain decorations in your tank such as Driftwood.

However, one should avoid adjusting the pH with chemicals. It is a very risky task. It may cause a pH spike, killing all the Discus instantly. Instead, it is wiser to let it remain constant to help your Discus adapt to it.

Chemical toxins

Water is a crucial part of keeping the discus fish in the aquarium. This is why care must be taken in terms of all water conditions which includes appropriate mineral levels, proper filtration, and even regular water changes.

The nitrite and ammonia levels should be 0ppm. If ammonia if present, you will observe your discus breathing heavily and a slight change in its colour. In such a case, water should be changed immediately. Nitrates should be less than 20 ppm in an ideal condition. Elevated levels of nitrates can be reduced by adding aquatic plants or removing any decaying matter in the tank.

At least 50% water should be changed twice a week, or preferably 25% thrice a week. This will reduce nitrates and replenish minerals. Water should be dechlorinated before it is changed. This is because Discus are messy eaters and contribute greatly to the nitrates in the tank.

Related questions

How to make sure the water in the tank remains at a safe temperature and pH? There are a variety of tools and instruments available in the market to help you maintain a constant and safe temperature & pH in your aquarium. These include; heaters, thermometers, filters, gravels, power heads, air pumps, plants, lights, and hoods. To avoid any inconvenience, research thoroughly before installing any of the above in your aquarium.

Does the size of my tank determine the maintenance routine? A common misconception is that larger tanks require twice the work. However, this is not true because if your fish requires a water change twice a week in a small tank, you will still have to follow the same routine if you shift them to a larger tank. Similarly, maintaining the water chemistry in a larger tank is somewhat the same as in a smaller one. It is a bit easier in the larger one as slight changes do not have considerable effects in its water chemistry.


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