Discus fish (Symphysodon)

Discus fish (Symphysodon) is an incredibly beautiful fish with very unusual body shape. The fish is often called a king of freshwater tanks and not in vain. Large, impossibly bright fish with lots of different colorings…so why not a king? Discus fish is leisured and stately as the king should be. This peaceful and graceful fish draws aquarists’ eye like no other fish can.

Discus is Cichlid family species and it’s divided into three subspecies, two of which have been known for a long time already and the third one has been discovered fairly recently. Symphysodon aequifasciatus and Symphysodon discus are the most well known discus fish species, which inhabit in central and low course of the Amazon River, they are very much alike as for the coloring and behavior. However, the 3rd subspecies Symphysodon haraldi has been relatively recently described by Heiko Bleher and it awaits further classification and acknowledgment.
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Sure, nowadays wildlife species of discus fish are much less spread, than species obtained by selective breeding. Even though this fish species has coloring that differs quite a lot from the wildlife species, it is less adapted to life in a tank, it prones to get ill more often and requires much more care. Moreover, discus is one of the most demanding tank fish, which requires stable water parameters, a spacious tank, quality feed and the fish itself isn’t a cheap one.

Inhabitance in the wild

The Amazon River basin biotopes change substantially during a year: when the rainy season comes in December the Amazon River floods. Tropical showers and ice water from highlands increase water stage in the streamway. Lots of tributaries change their streamline into the opposite one, till the overflowing river doesn’t flood a huge territory. Muddy and clayey water gets into the ponds with crystal clean water. The flooded forest that surrounds the Amazon River turns into one single slow flowing bog.

Rainstorms stop by May. The river water stops its ingress into the flooded forest and the water there gradually becomes clean and transparent. Since July and for several months later the water stage sufficiently decreases. A lot of separated waters and small streams appear, there the water becomes clean and obtains distinguishing dark color. Water parameters in such basins can reach maximum softness values, become aseptic with no electroconductibility. According to H. Bleher discus inhabits in black waters among riverside bushes. The waters bottom is covered with rotten leaves. The water is very soft and rather acidic. Roots of the riverside plants are under the water most of the year and serve as a shelter and spawning substrate for discus. When the water stage lessens, the fish leaves its hide-places and swims to the depth closer to the basins center.

Discus can’t be encountered in large rivers and very seldom it’s seen where the water flow is strong, it settles in lots of tributaries and streams. Thus, limited migration of isolated populations leads to the formation of certain features (coloring, first of all) even for comparatively small isolated groups.

In the wild the basics of discus diet is insect larvae and freshwater prawn. Together with discus you may also encounter the following:

  • Cichlides of Mesonauta, Heros, Crenicichla, Cichla, Geophagus, Satanoperca, Apistogramma, Acarichthys kinds
  • Different small tetras, catfishes, black ghost knifefish.
  • You may see piranhas, Leporinus, Myleus, Osteoglossum
  • An electric eel is discus main natural predator.

Appearance

Discus is a rather large fish with disc-shaped body. Discus body can grow to be 20-25 cm (8-10 in) long depending on its kind. This is one of the cichlids which has the most flattened body and it reminds a disc, which gave the fish its name. Right now it’s impossible to describe fish coloring, since there are lots of species with different coloring which were bred by the amateur aquarists. It’ll take quite a while just to try to name the types of the fish coloring.

However, in the process if selection this fish has not only got a bright coloring, but also rather weak immunity and liability to diseases. Unlike the wildlife fish species, selected species are more demanding and picky.

Types of discus fish:

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Difficulties in keeping

Discus is definitely for experienced aquarists, it’s decidedly not the fish for the beginners. The fish is very demanding, so even for an expert aquarist it can be quite challenging to keep it, especially to make it breed. The first difficulty owner faces is the fish acclimatization in a new tank. Adult fish takes its relocation more easily, yet even they are prone to get stressed. Large sizes, ill health, demanding to care and feed, high tank water temperature – all these issues you have to consider before buying your first discus. You’ll need a spacious tank, a very good filter, branded food and huge amount of patience. You have to be cautious when buying the fish, since it tends to get ill with white spot disease and others, and relocation will cause stress and stimulate the disease development.

Feeding

Diet is mainly live feed or it can be frozen feed. For example, tubifex, blood worm, brine shrimp, corethra, gammarus. However, professional fish keepers feed it either with branded feed, or with different meat farce which include ox heart, prawns and mussels, fish fillet, nettle, vitamins, different vegetables. Almost any professional aquarist has its own proved recipe and sometimes it consists of dozens of ingredients.

It’s important to keep in mind that discus is rather timid and a bit dumb; they can stay in some corner of the tank while the other fishes are eating. This is the reason why this fish is usually kept separately from others.

We’d like to mention also that protein rich leftovers which get to the tank bottom cause growth of ammonia and nitrates content in the tank water, which takes a toll on fish. You should either siphonage the tank bottom regularly, or use no bottom substrate for the tank, which is often done by the aquarists.

However, especially live blood warm and tubifex may cause both different diseases and foodborne intoxication of the fish, that’s why the fish is usually fed with minced meat or artificial feed.

Keeping in a tank

To keep discus you’ll need a tank of at least 200 liters capacity (52,83 gallons), but if you are going to keep more than one fish, the tank capacity should be much more. Since the fish is tall the tank should be quite long and high as well.

Powerful external filter is a must in this case, the same is about regular tank bottom substrate siphonage and weekly partial water renew. Discus is very sensitive to ammonia and nitrates content in tank water, just like to all water parameters in general and its purity. Although, the fish itself doesn’t produce a lot of waste, it eats mainly different kinds of forcemeat which crumbles quite fast in tank water and this way pollutes it.

Tank water should be soft and a bit acidic, as for its temperature – the fish requires hotter water than the majority of tropical fish does. This is one of the reasons why it’s difficult to choose discus tank mates. Water temperature comfortable for the fish is 28-32° C (82,4-89,6 F), ph: 6.0-6.5, 10 – 15 dGH. Under other tank water parameters this fish prones to get ill or it may even die. Discus is very timid – it doesn’t like loud sounds, sudden movements, knocking on the tank glass and restless tank mates. It’s desirable to place the tank with discus somewhere where it’ll be less disturbed.

Planted tanks will do for discus, if they have enough space to swim there. However, you have to consider that not all plants can stand water temperature higher than 28С, therefore it’s quite difficult to select proper plant kinds. Here are the following options you may consider: Didiplis diandra, Vallisnéria, Anubias barteri var. nana, giant ambulia, rotala indica (Indian toothcup).

Tank substrate can be of any kind, however, as a rule, the fish is kept in tanks with no plants or bottom substrate. By doing this you make the process of taking care about the fish much easier and reduce a risk of the fish getting ill.

When you first put discus into a tank, give the fish some time to recover from stress. Don’t turn on the light, don’t stand near the tank, put some plants or something else into the tank, which the fish can use to hide.

Scientific Name Symphysodon
Common Name Ramshorn snail
Tank size 200 liters (52,83 gallons) and more
Temperament Peaceful, timid
Diet Omnivorous
Temperature 28-32° C (82,4-89,6 F)
pH 6.0-6.5
Size 20-25 cm (8-10 in)

Compatibility

Unlike other cichlid species discus is a peaceful and good tempered one. It’s not a predator and it doesn’t dig tank substrate like other cichlids. Discus is a schooling fish so it prefers to stay in groups of 6 species at least and it hardly stands being alone.

The difficulty when choosing tank mates for discus is that the fish is slow, it eats slow and inhabits in water with rather high for other fish species temperature. Due to this and also to prevent the possibility of the fish infection, fish is often kept in a separate tank. But, if you still want to put some tank mates into the tank, you should consider the following: neon tetra, the Ram cichlid, clown loach, rummy nose tetra, congo tetra, cardinal tetra and different catfishes and put, for example, Pterygoplichthys gibbiceps to keep the tank clean.

Sex differences

It’s quite difficult to see between discus male and female, you can know for sure only during their spawning period. Some experienced aquarists can distinguish the fish male from the female by its head – the male fish has more receding forehead and full lips.

Breeding

If you aim to make your discus breed, so the more species are in a school, the better. You should buy at least 6-8 young species and hope that in time you’ll get at least one couple among them. There’s no need to interfere into the process of the fish couple formation – the fish will do it themselves. However, it is desirable to prepare a proper sized tank for them in advance, since yesterday’s juveniles will turn into large fish quite fast. Prepare a separate spawning tank in advance as well.

What should I do if fish couple eats its eggs? This is quite common phenomena when discus breeding and it is often observed among the young fish. Don’t hurry to break up the couple. It’s better to give it a chance to grow older. You have to let them show themselves as “parents”, usually after several unsuccessful spawning everything gets fine. You may also use a glass wall or some net to separate from the others the parent, who usually eats the eggs. Or you can cover the spawn with some synthetic net, through which the fish juveniles will be able to go out later. However, in this case the fish parents may completely lose their interest to the eggs. If nothing of these helps, then you should break up the fish couple after their 10-15 tries to spawn.

Should I continue tank water renews when the fish has already spawned?

For successful discus breeding water in the spawning tank should be very clean. If there is a possibility, stick to the routine schedule of water renews. Especially if the spawning tank is small sized (about 100 liters or 26,42 gallons). We can recommend you to continue water renews but in smaller amounts and more often. Surely, the spawning tank water parameters must be the same as the initial tank water has. In fact, this condition is rather difficult to fulfill. That’s why lots of professional breeders prefer to stop water renews in the spawning tank for some time.

Light in the spawning tank should be dim, but it should be on 24 hours a day during spawning. Any low powered lamp placed at some distance from the spawning tank will do for this purpose. We’d also like to remind you not to disturb the fish in the spawning tank by any other unnecessary actions inside it.

Water in the spawning tank has to be maximally soft (2-3 degrees) and slightly acidic (рН in the range of 6-6,2). In more hard and alkaline water the percentage of fertilized eggs significantly reduces. When pH value changes to more acidic one (close to 5.5), increase of the fish phys secretion was noticed. However, a list of other issues arises then.

Also there are known the cases of some fish species breeding in common tap water. Actually, we still don’t know for sure what causes unsuccessful spawning of discus. Sometimes in water which is proper for the fish spawning the results are rather doubtfully successful and vice versa, – in quite old water with large amount of organic wastes in it, with definitely not proper parameters one achieves 100 % juveniles yield. Any attempt to reproduce this success usually gives zero result.

One of the criteria to make this or that decision as for the water renews is the spawning tank size, where the fish has laid its eggs. In case of large sized spawning tank you have some spare space, which can be used. If the spawning tank is small, it’s obvious that the water will get spoiled faster and it’ll surely require renews. So more difficult it is to perform renews in this case without changing the water parameters in the end. And the latter affects adversely the eggs and larvae.

From all these sketchy facts, that don’t cover completely all the issues as for breeding, it becomes obvious how complicated the whole process is and why it still does not happen simple and easy on an industrial scale. Even in large Asian fish farms, where there are lots of tanks with discus with the same water parameters, still each fish couple requires custom solutions.