Caring For Discus Fish
Discus fish are now one of the most popular fish species that are kept in home aquariums and as methods for keeping them improve they are getting to be kept by some of the more inexperienced keepers with great success as more information is available for the keeper to research. There are many colour morphs and strains available nowadays. Most of these are the result of selective breeding and it is guaranteed that each of the new strains will have at least 3-4 different common names. But where do the original wild strains of Discus fish come from and what sort of conditions are they used to in their natural habitat, hopefully this article will provide a summary of the way to keep these beautiful fish and help you understand their origins.
Origins of Discus Fish
They originate from the Amazonian River Basins where they inhabit the Black water tributaries, often these waters can be murky especially in the rainy season but these conditions favour this fish as it is during the rainy season that Discus fish usually spawn their new broods. They can grow quite large, specimens up to 8” diameter are not uncommon especially if they are male and as mentioned any colour that you desire can now be found for purchase. The wild strains were plainer colours and possessed dark stripes down their bodies especially as juveniles, originally there were three main species and these were discovered in 1840 by Dr.Heckel, specimens of these were imported over to the USA originally and most of the main breeding programmes started there, nowadays they are bred all over the world. The three original strains discovered were Symphysodon aequifasciata (Green Discus), Symphysodon aequifasciata axelrodi (Brown Discus) and the Symphysodon aequifasciata haraldi (Blue Discus), the most common wild Discus fish imported nowadays is the Heckel which is still believed to be a mix of these original strains.
These fish are not a solitary species; they are found in large groups in their own habitat and as such always should be kept in a group in the aquarium. The demand for new strains by the hobbyist means that even the natural stripes that are used by the Discus are slowly disappearing to favour bright colours; the drawback is that the stripes are used by the fish as a means to communicate to each other. They do demand high water quality and even nowadays with the hardier strains, unexpected mortalities still occur leaving the keeper bemused as to where they went wrong. Never make the mistake of thinking that if you have tank bred specimens that they can tolerate a wider range of water parameters or quality, this is not true!
Setting up your Discus Tank
As mentioned above, Discus fish need to be kept in small groups of at least 6 fish. Each fish will need at least 10 gallons of water volume so the minimum size tank that you will need is 60 gallons and as they are a tall fish, the deeper the tank the better. Positioning the tank is also important as these fish are easily spooked, do not place the aquarium where there may be a lot of human traffic, this will cause the fish to become nervous and hide away a lot, the height of the tank position is also important, it needs to be at least near waist height, they do not like to see movement above the water surface and a pair of legs moving in front of the tank can also upset them. For setting up the display tank the substrate should be sand or fine gravel but do not make this too deep or toxic gases can get trapped in there, between 1-2 inches is fine. When the tank is up and running the substrate will need cleaning on a regular basis with a gravel vacuum or similar so bear this in mind when adding your décor. Planted tanks and Discus go hand in hand, Amazon swords, Vallisneria, Anubias, these all look effective in the display tank and add pieces of bogwood for décor, try to make it look random and not too uniform. There is a debate at the moment as to how high the lighting should be, subdued lighting was always favoured but keepers have now come to the conclusion that the Discus fish will get used to the lighting whatever intensity that you use, I can back this up from personal experience.
The heart of the display tank is the filtration system, it must be rated for the water volume that you are keeping, and all large cichlids are messy eaters and high waste producers. The filter should be capable of performing mechanical filtration, this is performed by sponges or similar that will trap debris as it passes through, if this is allowed to say in the tank it cam break down and foul the water. The second stage is the biological filtration where the beneficial bacteria colonise the filter media and convert ammonia and nitrites into nitrates. Chemical filtration is optional and is most often only needed to remove medications from the tank, if you do prefer to add carbon to the filter remember to change it at least once a month to prevent it from getting saturated and leaching toxins into the water.
Most Discus fish that are tank bred are quite happy with a pH that ranges between 6.5-7.5 so if your mains waster falls into this range do not try to keep altering the level just because someone has said they need it below 7.0, the fish will suffer more if it keeps fluctuating so settle for the level that it is naturally. Discus fish do require a certain level of minerals in the water so aim for a KH level just above 4 to keep the pH from crashing and set the GH to a similar level.
At one time it was thought that Reverse Osmosis units were the only chance we had to keep the Discus in a high enough water quality but it has been proved that if the water is treated with a suitable conditioner then this is not always the case, the higher north you are up the country the harder the water but doing a partial mix of RO water with treated mains water should bring this down to an acceptable level.
Water changes are very important when keeping Discus fish, at least twice a week and each time changing 25% of the water volume will keep it re-mineralised and clean. Use the gravel vacuum on a regular basis to keep the substrate clean and perform normal tank maintenance to keep the tank glass clean. Temperature wise I ran all of my tanks at 29 °C, this seemed to suit the Discus fine.
Acclimatising the Discus fish to the tank can be tricky if you try to perform it too quickly, taking longer is less stress on the fish and the keeper. These fish do not take well to sudden changes in water parameters so I would normally acclimatise Discus for at least one hour before adding them to the tank, another golden rule is to never add them to a new tank set up either. Cycle the tank and add some tetras or other hardy fish to keep the filters running, bottom feeders such as Corydoras can also be added but do not add the Discus until the tank has been running for at least 6 months, by this time the tank will have matured and the water parameters will be constant. Once the have been acclimatised into the tank they will be skittish and hide away for a few days, this is perfectly normal and eventually they will recognise the hand that feeds them and swim to the front of the tank as you approach.
Tank Mates for Discus Fish
Some tank mates for Discus fish have been mentioned above but this section will deal in more detail suitable species. When selecting tank mates always remember that the aquarium is running at a higher temperature to most tropical tanks, this can limit your choice.
I have always used Corydoras for the bottom feeders, a small group of 6 specimens is ideal and they will help to keep the substrate clean. Other bottom feeders that I have also had a great success with are Ancistrus sp. (Bristlenose Catfish). Many keepers claim that catfish will latch onto the Discus as they develop a taste for the slime that the Discus produce, I have never had a problem with this in 20 years of keeping these fish.
For middle swimmers I have always added Bolivian Rams or Blue Rams, these need to be kept in pairs and are not overly aggressive but can be slightly territorial if they go into spawning mode. Other middle swimmers that I always add are Cardinal Tetras, adding a shoal of these containing about 20 specimens sets off the aquarium and adds a lot of colour.
Feeding Discus Fish
Discus fish are primarily carnivorous but they do require a varied diet that is high in protein to meet all of their needs. For the staple diet always use a quality flake, cheaper flakes may seem a good buy at the time but they do not contain all of the nutrients that higher quality brands do, I found the best result came from using Tetra Prima granules, discus like to feed as the food sinks midway and these granules were ideal for that. Live and frozen foods should also be offered 2-3 times per week. Brine shrimp and Bloodworms are fine but always rinse them before feeding, it will take the Discus longer to feed than a lot of other fish as they like to graze slowly so let them feed for 10 minutes and then siphon any uneaten food out of the tank.
If the tank is set up correctly and the water quality is kept at a high level then caring for these beautiful fish should not cause too many problems, some keepers are even lucky enough to finish up with pairs that start to spawn but that subject can be quite detailed so will be included in a separate article.