Discus, and everything you need to know about them…
Discus is one of the most beautiful aquarium fishes. Today, there are many color variations of discus in aquarium keeping, from which you can choose the most suitable fish to your taste. Currently, there is a very large number of different discus species, with most of them being artificially bred forms characterized by various color shades. This does not mean that their offspring will exactly repeat the parents’ coloration. However, their cost is significantly higher, and they are less resistant to diseases. Therefore, for beginner enthusiasts, it is advisable to start by purchasing discus species widely distributed in their natural habitat. Today, discus fish are quite common in amateur aquariums, but groundless rumors still trail them as extremely moody, sickly, and timid fish.
Most often, discus are kept in species aquariums, i.e., those inhabited exclusively by discus. An aquarium of less than 100 liters is practically unsuitable for keeping discus. It can only be considered as temporary housing for very small fish or used as a quarantine tank. In general, to keep discus, it is advisable to purchase aquariums with a capacity of 200 liters and above. Care for smaller tanks must be especially thorough, but maintaining stable conditions in them is still quite problematic. The larger the aquarium volume, the easier it is to keep them, i.e., maintain constant conditions. Fine gravel can be used for the substrate, although many aquarists prefer keeping discus in a bare-bottom aquarium.
According to numerous observations by professionals, discus grow noticeably faster in large volumes, not to mention other advantages of a large reservoir. Simply put, a standard 200-250 liter aquarium of a classic or near-classic shape is the minimum volume that will not soon lead you to buy a new aquarium and a more powerful equipment set for it.
And the larger the aquarium size, the faster your pets will grow, reaching a larger size, the more stable the aquatic environment in the aquarium will be, and the more freedom you will have in implementing your design ideas for aquascaping. Aquariums should be tall, no lower than 50 cm. If you are not constrained by living conditions and the aquarium size does not have strictly specified parameters, preference should be given to an aquarium with greater depth. The length of the aquarium is not as important as in the case of active schooling fish.
Discus is a schooling fish, so it is best to keep them in groups of at least 5 individuals. If you plan to keep 8-10 specimens, the aquarium must be equipped with a fairly powerful filter. In addition, do not forget that new specimens you plan to introduce into an aquarium where fish are already living must first undergo quarantine. The number of discus you plan to keep in your aquarium will depend on its size.
It is necessary to provide 35-40 liters per adult specimen (15-20 cm), though 50 liters or more is preferred; 10-15 liters is enough for a small fish (5-6 cm), and 20-30 liters for juveniles (6-10 cm). But we must not forget that discus grow quite fast (reaching almost their maximum size at 12-15 months of age), and these harmless babies will require additional volume in half a year. Therefore, it makes sense to calculate based on adult fish right away.
Discus is a fish for aquarists who are ready to spend their time and energy on keeping them. Discus has long acquired a reputation as a difficult-to-keep, delicate, and moody fish, but the truth is that with proper care, all the above-mentioned problems disappear. Indeed, at the current level of aquarium development, not only keeping but also breeding discus has long ceased to be an insoluble problem. Regular massive water changes combined with a relatively high temperature and suitable food are the main factors in this matter.
Difficulties usually arise only when keeping wild-caught specimens, and they are mainly associated with water preparation close to natural conditions – soft, low-mineralized, saturated with tannins and humic acids. Tank-bred discus are significantly less demanding of the chemical composition of water and, as a rule, can be kept without major problems in ordinary tap water with a wide range of hardness and acidity. By the way, natural discus, with a relatively long adaptation to ordinary water, grow and develop quite normally, though their water quality requirements remain higher.
Discus and other fish.
There are many different opinions on this matter, but the answer of the overwhelming majority of professionals is a categorical “no”. And it is not about the need to maintain a high temperature normal for discus, which most fish simply cannot withstand. Of course, you can find a dozen or two fish for which a temperature of 30 degrees is quite acceptable (for example, the blue ram cichlid or angelfish). Keeping even larger fish with discus is generally undesirable. You should not choose aggressive fish as neighbors, especially if your discus are still young.
There are several main reasons: • Discus eat quite slowly, and in the presence of more agile fish, they will get a reduced portion of food; • The impossibility of preventive treatments in a general aquarium, since raising the already high temperature by an additional 3-4 degrees will not be tolerated by other aquarium inhabitants; • Frequent water changes will likely negatively affect the well-being of most other fish; • Practically all fish are carriers of common fish diseases, even if they do not often get sick themselves. The immune system of discus, as a result of many years of breeding, is very weakened, and the presence of an outside infection carrier in the aquarium will sooner or later affect their health. • Despite their external nobility, discus can be aggressive towards smaller fish.
However, they can also get along with other species if you wish. Those who can be recommended for co-keeping with discus are bottom-dwelling catfish that clean up leftover food and thus bring undeniable benefits to the aquarium as a whole. First of all, the sailfin pleco (*Pterygoplichthys pardalis*), which feels great in conditions of elevated temperature and intensive water exchange. But they constantly uproot plants. Others keep cardinal tetras, black mollies, and sailfin mollies, which not only withstand high temperatures but also reproduce and even manage to grow alongside discus.
A school of *Corydoras* is also a great fit, as they clean up fallen food. Most importantly, they are very useful because they eat small algae off plants. The so-called SAE (Siamese algae eaters) are useful; 1 specimen per 100 liters is recommended, but they are very active and in larger numbers might bother discus. Avoid fast-swimming fish. Do not keep them with *Gyrinocheilus aymonieri*, which may latch onto the large body of a discus. Unfortunately, angelfish (*Pterophyllum*) are often carriers of parasites that can be fatal to discus.
Introduction of A-numbers for Apistogramma. List of Apistogramma numbers. 
