Having installed an aquarium at home, every aquarist is faced with the question of How Many Fish In Tank 5, 10, 20, 30, 40, 50, 100, 150, 300 Litres?
There are several approaches to determining the number of fish that can be populated in an aquarium:
- by the number of liters per centimeter of body length of the fish;
- depending on the surface area of the water;
- taking into account the required living space for each individual type of fish.
Regardless of which approach will be used, the main criterion for the correct determination of the number of fish will be the health, appearance of pets, their activity and ability to reproduce offspring after the aquarium is populated and the biological balance of the system is established.
Table of Contents
how many fish in tank? Fish stocking
The first thing you should pay attention to when calculating the number of fish is the volume of the aquarium and its geometric dimensions. In the literature, one often encounters a rather primitive calculation 1-2 liters of water are needed for 1 cm of fish length. This method can only be used with caveats:
- the calculation takes into account the size of adults, and not the purchased young;
- the aquarium must be equipped with a water treatment system and an aerator;
- it is necessary to take into account the layer-by-layer filling of the aquarium, especially when filling aquariums from 30 liters – so that in the end it does not turn out that most fish prefer to spend time in the middle layers, and the bottom and surface layers are empty;
- do not forget that large fish produce a lot of waste products, which in small aquariums can quickly make the water unusable;
- from the nominal volume of the aquarium, the volume of soil, decorations, if any, should be subtracted – approximately 15%.
You should also take into account the geometric dimensions of the aquarium – the ratio of width, length and height. For the most part, this indicator will affect the overall aesthetic perception of a filled aquarium, for example, fish with a high laterally compressed body (gourami, angelfish, Sumatran barbs) look more advantageous in aquariums where the height exceeds or equals its length, and the width is small (screen aquarium) . Elongated fish (danios, swordtails) look winning in low long aquariums. For a round aquarium, it is worth giving preference to fish with a voluminous body – varieties of goldfish – telescopes, wauletails.
The disadvantage of this approach to calculating the number of fish in an aquarium is that it does not take into account the characteristics of different breeds, providing only a minimal space for physiological health. Often this leads to the fact that some specimens can show aggression towards their neighbors (for example, the betta fighting fish), less energetic fish will clog in the corners and in the algae bushes.
types of aquarium fishes based on size per liters Fish Tank
| types of aquarium fishes based on size | Water volume, l |
| Small – up to 6 cm in length: neon, guppies, platies, some types of barbs, zebrafish, cardinal. | 5-7 liters per couple. |
| Medium – from 7 to 12 cm in length: swordsman, black molinesia, Sumatran barb, parsing, cockerel, speckled catfish, macropods, gourami. | 30 liters per couple. |
| Large – 15-20 cm in length: goldfish and their varieties, pearl gourami. | 40-45 liters per couple. |
| Very large – over 20 cm in length: discus, African and American cichlids, Indian knives, modesta botsia. | From 150 liters per couple and above. |
How to determine how many fish are in a tank?
When populating an aquarium with fish, you can also focus on the surface area of the water. The calculation of the area is quite simple:
- for square and rectangular aquariums, multiply the length by the width;
- for round ones – 3.14 * R 2 , where R is the radius of the aquarium.
Further focus on the rule: small 2-5 cm fish with a narrow body require 90 cm 2 of area, larger specimens or those with a rounded body shape – 150 cm 2 .
The downside of this approach is that, like the first option, it does not take into account the characteristics of various fish species, such as the amount of waste products produced by the specimen, as well as the possibilities for improving gas exchange with forced aeration.
Calculation of the number of fish, taking into account the characteristics of the species
Before you buy fish and populate an aquarium, you first need to decide on the species composition of the fish house. Ideally, having compiled a list, show it to an experienced aquarist who will be able to figure out how correctly the pets are selected, taking into account:
- conditions of detention (similar temperatures and pH of water, hardness);
- the nature of the selected species – the absence of aggressive breeds, differences in temperament (for example, it is difficult for quiet and calm guppies to get along in the same aquarium with active and frisky Sumatran barbs, it is generally recommended to keep males apart from all fish);
- separation of the inhabitants of the aquarium into layers – 25% should fall on the upper and bottom layers, 50% – on the middle;
- schooling or individualism of fish – species such as zebrafish, guppies, neons feel good in flocks of 6 specimens.
It is very important to select fish of different breeds responsibly.
If there is no one to get qualified advice from, then you should study the information on each species in as much detail as possible, and even then determine the number of fish and their species composition.
how many fish in tank less than 5 litres?
It should be noted right away that keeping fish in such microaquaria is a very troublesome business. The balance of the system is very difficult to achieve, it takes a lot of strength and patience to clean the aquarium, change the water (at least 4 times a week). You can plant a couple of guppies or one cockerel in such a small volume. The cockerel will feel great, but the guppies will quickly breed, and it will become crowded in the tank.
Aquariums smaller than 2 liters are not populated with animals, with the exception of some types of snails.
Interesting! in a volume of 10 ml of water, they managed to place a nano-compressor, small cladophora bushes and zebrafish fry.
how many fish in a 5 litre tank?
Very small aquariums of 5 liters are very difficult to populate with fish. The main difficulties lie in maintaining the biological balance and the necessary temperatures, which is more difficult to do in a small volume than in a large one.
Therefore, for a 5-liter aquarium, it is better to choose unpretentious peaceful small fish – a couple of guppies or a couple of swordtails. Black mollies will look spectacular in a small aquarium, but they are more whimsical to the conditions of detention than the listed fish.
If there is a desire to keep larger fish in a 5-liter aquarium, then you can populate it with a beautiful specimen of a goldfish, or gourami.
Important! Please note that large fish do not always look good in small containers. Therefore, the rule is more often used – small aquariums for small fish, large ones for large ones.
how many fish in a 10 litre tank?
You can diversify the species composition of the aquarium by 10 liters compared to a 5-liter aquarium with bottom fish. Spotted catfish get along well with most species, so a couple of these bottom cleaners will come in handy.
One gourami or a family of cockerels (a male and a couple of females) is well suited for living in the middle layer of an aquarium of 10 liters. It would be quite nice in such a volume and a flock of neon fish, swordtails, guppies, mollies. You can take a couple of all these fish, but they feel more comfortable in flocks of 5-7 pieces, so for such aquarium volumes it is better to stop at one species.
Important! To populate aquariums with a small volume of 10-30 liters, it is better to select small-sized fish – no more than 4-5 cm in length.
When calculating the number of fish for small aquariums, it is important to take into account other inhabitants, for example, large snails. They also produce waste that pollutes the system, so snail populations need to be kept under control.
what fish can i have in a 10 litre tank?
| Types of fish | Approximate number of fish, pcs. |
| Guppy | 4 |
| Mollies | 1 |
| Pecilia | 1 |
| barbs | 1 |
| Danio | 2 |
| Cardinals | 2 |
| Lyalius | 2 |
| Fighting fish (cockerels) | 2 |
| Tetradons dwarf | 1 |
| Apistograms Ramirezi | 1 |
| neon | 1 |
| Ornatus | 1 |
| Ternetia | 1 |
| tetras | 2 |
| Flashlights | 2 |
| Speckled corydoratus catfish | 1 |
how many fish can i have in a 20 litre tank?
For 20-liter aquariums, it is already safe to populate both the upper layer of water and the middle and bottom ones. If we take as a basis the species and quantitative composition of an aquarium of 10-15 liters, then 2-3 zebrafish can be added to a 20-liter one, but they may be too active for such a small aquarium.
A pair of medium-sized labyrinths – gourami, are also well suited for keeping in a 20-liter aquarium.
You can keep 1 goldfish, or its varieties a veiltail, a telescope, but you need to understand that in such small containers, these species will never grow to the normal size of an adult.
Important! Most often, small aquariums are bought for children, believing that it will be easier to care for them, but this is not so! All small aquariums require very frequent cleaning, good aeration that does not create currents, and cleaning, otherwise the fish can die very quickly. Therefore, when choosing an aquarium for a child, it is better to stop at easier-to-care containers of 50-60 liters.
what fish can i have in a 20 litre tank?
| fish for 20 litre tank | Approximate number of fish, pcs. |
| Guppy | 8 |
| Mollies | 1 |
| Pecilia | 2 |
| barbs | 1 |
| Danio | 4 |
| Cardinals | 4 |
| Gourami | 2 |
| Lyalius | 4 |
| macropods | 1 |
| Fighting fish (cockerels) | 4 |
| Tetradons dwarf | 2 |
| Apistograms Ramirezi | 2 |
| neon | 8 |
| Ornatus | 8 |
| Rhodostomus | 6 |
| Ternetia | 2 |
| tetras | 4 |
| Flashlights | 4 |
| Speckled corydoratus catfish | 1 |
| swordsmen | 2 |
how many fish in a 30 litre tank?
In such an aquarium, you can already turn around – make more flocks of fish, since most of the small fish look good among their relatives – about 10 neon fish and about 6 thorns, a couple of catfish. You can diversify the species composition with shrimp; most calm, medium-sized fish get along well with them.
You can populate the aquarium with a flock of 3-5 barbs, not forgetting that these bullies like to leave silent guppies without fins.
Most often, aquariums up to 30 liters are considered by professional aquarists only as spawning, or for rearing young animals, which will then be transferred to a large house. Therefore, such aquariums do not shine with a variety of species – for keeping them it is necessary to select the most unpretentious fish.
what fish can i have in a 30 litre tank?
| Types of fish | Approximate number of fish, pcs. |
| Guppy | 12 |
| Mollies | 2 |
| Pecilia | 3 |
| barbs | 2 |
| Danio | 6 |
| Cardinals | 6 |
| Gourami | 2 |
| Lyalius | 6 |
| macropods | 2 |
| Fighting fish (cockerels) | 7 |
| Tetradons dwarf | 2 |
| Apistograms Ramirezi | 3 |
| neon | 12 |
| Ornatus | 12 |
| Princesses of Burundi | 1 |
| Rhodostomus | 8 |
| Ternetia | 3 |
| tetras | 6 |
| Flashlights | 6 |
| Speckled corydoratus catfish | 2 |
| swordsmen | 3 |
how many fish in a 40 litre tank?
For aquariums of 40 liters, it is already possible to select a wider range of species, including larger specimens: various types of gourami, except for large pearl ones, dwarf tetrodons, laliuses, macropods. A couple of large fish, a couple of bottom catfish and a flock of 5-7 small fish – guppies, neon fish – is quite a sufficient number of inhabitants of an aquarium of 40 liters.
Important! Since small aquariums are easy to overpopulate with fish, it is recommended to buy and add them to the aquarium in parts – for example, they bought a flock of guppies – settled in, waited 2-3 days – bought gourami – settled in, waited again. During this time, you can take a closer look at how the pets feel, how harmoniously the aquarium looks with the already hooked fish and, if necessary, stop and not buy the next batch.
This method is difficult to apply only in cases of buying young animals, when the fish have not yet reached adult size.
what fish can go in a 40 litre tank?
| Types of fish | Approximate number of fish, pcs. |
| Guppy | 16 |
| Mollies | 3 |
| Pecilia | 4 |
| barbs | 2 |
| Danio | 8 |
| Cardinals | 8 |
| Gourami | 3 |
| Lyalius | 8 |
| macropods | 3 |
| Fighting fish (cockerels) | 10 |
| Tetradons dwarf | 3 |
| Apistograms Ramirezi | 4 |
| neon | 16 |
| Ornatus | 16 |
| Princesses of Burundi | 1 |
| Rhodostomus | 10 |
| Ternetia | 4 |
| tetras | 8 |
| Flashlights | 8 |
| Speckled corydoratus catfish | 4 |
| swordsmen | 3 |
how many fish in a 50 litre tank?
In aquariums of this size, it is already permissible to keep one labeo, a couple of flocks of small fish in 7-9 specimens, 3-4 catfish. It must be taken into account that if live-bearing animals, such as guppies, swordtails, malenesias, are kept together with large fish, then large specimens will be happy to eat fry, considering them food, so special jigger for fry will be needed.
A good water treatment system and more powerful aeration than in smaller aquariums allow a 50-liter aquarium to be stocked with more fish than is calculated.
what fish can go in a 50 litre tank?
| Types of fish | Approximate number of fish, pcs. |
| Guppy | 20 |
| Mollies | 4 |
| Pecilia | 6 |
| barbs | 4 |
| Danio | 10 |
| Cardinals | 10 |
| Goldfish | 1 |
| Gourami | 4 |
| Ctenopoma | 1 |
| Lyalius | 10 |
| labioses green | 1 |
| macropods | 4 |
| Fighting fish (cockerels) | 12 |
| Tetradons dwarf | 5 |
| Apistograms Ramirezi | 5 |
| neon | 20 |
| Ornatus | 20 |
| common piranhas | 1 |
| Princesses of Burundi | 2 |
| Rhodostomus | 12 |
| Ternetia | 5 |
| tetras | 10 |
| Flashlights | 10 |
| Acanthophthalmus | 1 |
| Ancistrus | 2 |
| Speckled corydoratus catfish | 5 |
| Badis | 2 |
| swordsmen | 4 |
how many fish in a 100 litre tank?
Aquariums with a volume of 60 to 100 liters are already large enough to contain larger fish with a body length of 15-20 cm. When calculating the number of inhabitants, it is better to adhere to this principle – first choose large breeds from 2 to 4 pieces, depending on the volume (this can be gourami, cichlids, goldfish, labeo), and then they pick up several types of bottom fish and several top-level fish, buying them in flocks, and always taking into account compatibility with the selected large fish.
In this volume range of 60-100 litres, it is very easy to get carried away and overcrowd the tank, especially when young are bought initially and until they grow up, the tank looks empty. It is important to clearly define the species you want to keep and stick to your choice, otherwise the aquarium will turn into a “fish hostel” with an endless flickering of all kinds of shapes and colors. Under such conditions, the fish will suffer from constant stress, which will affect their appearance and well-being.
Be sure to take into account that large fish tend to choose a corner to their liking and protect it from the invasion of strangers, so the corner, for example, occupied by a pair of angelfish, must already be deleted from the total volume of the inhabited territory. Barbs, on the contrary, tend to settle throughout the aquarium, haunting slower fish, starting fights and bullying everyone and everything.
what fish can go in a 100 litre tank?
| Types of fish | Approximate number of fish, pcs. |
| Guppy | 45 |
| Mollies | 12 |
| Pecilia | 12 |
| barbs | 10 |
| Danio | 20 |
| Cardinals | 20 |
| Goldfish | 2 |
| Gourami | 7 |
| Ctenopoma | 2 |
| Labeo | 2 |
| Lyalius | 20 |
| labioses green | 2 |
| macropods | 10 |
| Fighting fish (cockerels) | 25 |
| Tetradons | 2 |
| Tetradons dwarf | 10 |
| Apistogramma cockatoo | 4 |
| Apistograms Ramirezi | 10 |
| neon | 35 |
| Ornatus | 35 |
| common piranhas | 1 |
| Parrot | 1 |
| Princesses of Burundi | 4 |
| Pseudotropheus | 2 |
| Rhodostomus | 24 |
| Ternetia | 10 |
| tetras | 20 |
| Flashlights | 20 |
| Acanthophthalmus | 2 |
| Ancistrus | 2 |
| Julidochromis Regan | 1 |
| Speckled corydoratus catfish | 10 |
| Sac-gill catfish | 1 |
| Catfish Tarakatums | 1 |
| Badis | 4 |
| swordsmen | 6 |
how many fish in a 150 litre tank?
In large aquariums from 150 liters, it is better to keep large specimens of fish – cichlids (Acara, cichlosoma), goldfish, Labeo, from the bottom – Ancistrus. Small breeds will simply get lost in a large aquarium.
In a 150 liter aquarium you can keep:
- up to 10 pieces of small cichlids or 8 pieces of large ones;
- labeo 4-5 pieces;
- large specimens of goldfish – 3 pieces (their smaller number compared to other species is due to the fact that they produce a lot of waste products, which upsets the balance in the system);
- large specimens of pearl gourami 8 pieces;
- a couple of large catfish, such as sackgill catfish.
It should be borne in mind that the actual volume of a large aquarium will always be less than the declared one by even more than 15%, since in large aquariums it is customary to place more decorations, snags, stones, which also takes up a certain volume.
In aquariums of 200 liters, you can already accommodate a couple of discus. It is not recommended to add someone else to them, except for bottom catfish, since discus require high temperatures, which is not always good for other fish species.
In a 300 liter aquarium, discus can be diluted with a flock of iris – 3-5 pieces.
how many fish in a 300 litre tank?
Great attention should be paid to the selection of fish in such large aquariums. Most of the specimens, having reached their adult size, will eat everything that they can get into their mouths, so it is not worth “dilute” the inhabitants of the aquarium with small fish – they will all turn into food. Therefore, it is worth stopping at one species and populating the aquarium with the number of individuals that the volume allows.
Suitable Fishes for Stocking 300 litre tank:
- pterygoplix brocade;
- astronotus;
- African cichlids;
- silver arowana;
- Indian knives;
- discus,
- large sucker catfish.
All these fish grow to very large sizes, so they require from 100 to 300 liters per specimen.
Often, with a capacity of more than 300 liters, the aquarium is made marine and populated with fish characteristic of coral reefs – clown fish, surgeon, yellow zebrasoma, sapphire chrysiptera. The number of fish in a marine aquarium is calculated as follows: 35 liters of water per 10 cm of medium-sized fish and 5 cm of large ones.
Why it is not recommended to overpopulate an aquarium?
Looking at the abundance of fish species offered in pet stores, I want to collect them all, because there are never too many pets. But the trouble is that an overcrowded aquarium is very bad, and first of all for the health and life of the fish.
A large number of inhabitants will lead to the fact that waste products will accumulate in the aquarium, there will be not enough oxygen in the water, the water will be saturated with nitrites, ammonia and other nitrogenous compounds, which are the decay product of food residues and feces.
Such an unbalanced habitat will result in fish that are dim in color, do not grow to the size characteristic of the species, and in most cases will not be able to breed, or the offspring will be weak and unviable.
signs overcrowded fish tank
Overpopulation of the aquarium is very harmful to the health of the fish.
The main signs that the aquarium is overcrowded:
- pale dim color of fish
- gasping for air and finding the fish mostly near the surface is a clear sign of lack of oxygen
- the size of adult fish does not meet the physiological standards for the breed, the young do not gain weight.
What happens if you add too many fish at once?
Often, overpopulation of the aquarium leads to the death of fish, especially at night, since at night the algae do not release but consume oxygen and its deficiency becomes more acute. Also, with a high density of aquarium inhabitants, outbreaks of diseases occur that can lead to the death of most pets.
How do you manage overcrowded aquariums?
Part of the problem of aquarium overcrowding can be solved by a good water purification system or by installing a flow-through water change system when part of the water in the aquarium is constantly replaced with fresh water. But it is better to prevent such a situation and limit the number of inhabitants of the aquarium.
