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What size should an aquarium for discus fish be?

Large fish need a large enough tank. Size of the aquarium for discus plays an important role for two main reasons – first reason is that, like most cichlids, discus are territorial fish. In an aquarium large enough, each adult discus (or matched pair) has more or less constant territory and tries to defend it against other fish, even stronger than them, which can be easily observed during feeding.

If the tank is too small, weaker fish can sometimes even die because of stress caused by harassment by the stronger fish, which is nothing very unique in the animal world. This is especially important if you have only one main aquarium, and you can not 100% optimal match of individual fish in terms of temperament. In such case, you absolutely must avoid overstock. The second argument for a specific size of a discus aquarium is far more banal – discus fish have a powerful metabolism and healthy specimens are ruthless in providing reasons for water changes and cleaning the bottom of tank. In a large aquarium system is easier to handle this, while in the small tank, apart from the aforementioned psychological discomfort of fish, the aquarist will have to keep a constant struggle to maintain proper water parameters – whether this is the matter in the aquarium hobby?

For each adult discus should be allocated to 50l of water or more. Adult discus is a fish with a diameter of 16-22cm. This does not mean, however, that such quarantine tank for one adult discus may be 50 liters capacity – absolutely smallest tank capacity that must be taken into account for discus is 100 liters. Above figures are approximate, but I do not recommend downward deviations.

Discus fish are gregarious, but such behavior is fully disclosed in a sufficiently large tank (or under stress).  Therefore, if we consider the stock a minimum of 5 fish (this is quite a few), so while preserving the principle of assignment for each adult fish at least 50 liters of water, the math is inexorable – we get a result equal to 250 liters of water, where with the thick substrate and some roots and plants, an aquarium with dimensions 120x50x50 cm (300l gross) hardly fulfill this requirement. In such a tank can live up to 4-5 adult discus.

It is quite a widespread view that one should buy a larger quantity of young discus and when they grow leave the target number of selected fish. This reasoning is correct, but that does not mean, however, that such a procedure is appropriate in the case of the said 300l decoration tank. Young discus require an intensive feeding and demand that from aquarist. The effect may be that the fish before they finally grow up, aquarium substrate stores a huge amount of dirt and tank restart will be needed. If the aquarist disregard the first signals, then will select the fish and leave the tank in such a state with a smaller cast – that can lead to disaster that is the culmination of the process of excessive pollution of aquarium, begun long before. One day the view can be as follows – dark, panting, frightened discus fish and rotting plants. And this is supposed to be decorative aquarium.. To avoid the described situation, you should really take seriously the principle of non-overstock of decorative aquarium and grow young discus in a bare bottom tank with a sponge filter and aeration. To maintain the safety margin, please take into account as a decorative aquarium for discus, tank with dimensions similar to the standard 150 x 50 x 50 cm, and really allocate a minimum of 50 liters of water per fish.

When discus aquarium is too small

Discus introduced to too small decorative aquarium containing gravel substrate and possibly  plants in many cases results in a similar scenario: At the beginning all is well – young fish eat and grow. After some time, however, discus begin to behave strangely, become timid, their breath is fast not only after eating. Discus longer be hidden in aquarium corners  before they start to swim freely. At this point the novice discus lover now seek advice on Internet forums and in consultation concludes that .. time for the treatment of fish.
Well, this topic is quite interesting, but will be discussed in another article (“old tank syndrome”).