The Right Fish Stock For An Aquarium

The underwater world fascinates many people and aquaristics are also enjoying ever-growing popularity. Numerous aquarium tanks in almost all sizes and in various shapes set no limits to the imagination and beautiful and diverse landscapes of plants, roots, and decorative items are created, which attract everyone’s attention.

In addition to plants and the like, various fish are usually kept in an aquarium. Whether species tanks, natural tanks, the often and gladly used community tanks or other variations, freshwater aquaristics, or rather seawater, it is important to meet certain criteria when stocking fish. It is clear that when choosing the new fish stock, not only does one’s own taste play an important role but also the different needs of the fish are very important so that they can continue to live healthy and long lives. In this article, we will show you how to find the right fish stock for your aquarium and what to look out for.

A few rules beforehand

An aquarium cannot be filled with fish at will. For example, the fish have different requirements when it comes to the water values prevailing there, some species cannot be socialized and others need a lot of space because they have reached a certain size in a few years. Each fish has a different way of life, which should definitely be taken into account for the fish that will live in the aquarium in the future.

Rules of thumb:

For fish with a final size of up to four centimeters, at least one liter of water should be available per centimeter of fish. In an 80-liter aquarium, means that a total of 80 centimeters of fish can be kept in it. However, it must be taken into account that the fish also grow, so that the final size must always be assumed.

Fish larger than four centimeters need even more space. For fish species up to a size of 4 – 8 centimeters, there must be at least two liters of water for one centimeter of fish.
Fish that get even bigger and reach a final size of 15 centimeters need three liters of water for one centimeter of fish.

  • up to 4 cm of fish, 1 liter of water per 1 cm of fish applies;
  • up to 8 cm applies 2 liters of water to 1 cm of fish;
  • up to 15 cm applies 3 liters of water to 1 cm of fish.

The dimensions of the pool

In addition to the amount of water, the edge length of the aquarium must also be considered for larger fish. However, some fish species not only grow in length but also in height, as is the case with the majestic angelfish, for example. As a result, not only the edge length is important, but the pool must also have sufficient space in terms of height.

Breeding of fish

While some aquarists who are new to the area may assume that dying off will only minimize fish numbers, there are some species of fish that reproduce quickly and profusely. These include, for example, the very popular guppies or mollies. Of course, this means that the aquarium can quickly become too small because even the small baby fish grow up quickly and begin to breed with each other. In this case, it is best if you don’t let it get that far in the first place, because since the fish that are produced also breed with each other, inbreeding quickly occurs, which can lead to dangerous deformities.

Avoid turf wars

Furthermore, the territorial behavior of some species must be taken into account, because they fight for their territories, which can quickly lead to injuries to other fish. The swimming behavior of the different fish species is also important when choosing the right stock.

Males and females

With many fish species, it is, unfortunately, the case that the males tend to fight among themselves, and experts, therefore, advise keeping a certain number of females for one male. This is the case, for example, with guppies. Here you should plan three females for one male so that the males do not fight among themselves and the female fish are not constantly bothered by the males. The latter can lead to the females being under stress, under which they can even die.

Aquarists who do not want to have offspring should keep either only male or only female fish. Since male fish, as already mentioned, tend to fight among themselves, it is advisable to take the females instead. The disadvantage here, however, is that the females of many fish species are unfortunately not colorful, while the males are. The best example is the guppies, where the females appear monochromatic and, in contrast to the males, rather boring. The male guppies are the fish with brightly colored tails that make every aquarium an eye-catcher.

Still other fish should only be kept in pairs, so keeping only males or females is not recommended. As a rule, however, these are species that do not tend to reproduce, which include, for example, the dwarf gouramis.

In the case of other species, it is not even possible to distinguish between the sexes at first glance.

Special demands of the fish in the aquarium

Many fish species have very special requirements for their habitat. This does not only refer to the water values ​​that should prevail in the pool. The temperature also varies from species to species, so that some fish prefer it cool and prefer a maximum temperature of 18 degrees. Still others prefer it warmer, such as catfish. In this species of fish, the minimum temperature is already 26 degrees. The individual fish should therefore have the same requirements in this regard.

Furnishings are also very important. Some species of fish need special items to fade, such as Discus, which needs special clay spawning cones. Catfish need caves again to hide or lay eggs. The roots are also vital for catfish and are used for the digestion of the animals. Without a suitable root, some catfish species, for example, would die.

Inform beforehand

In order not to make any mistakes, it is particularly important to obtain detailed information on the individual species in advance.

This relates to the following criteria:

  • how big is the fish?
  • from how many liters of water can this fish be kept?
  • What water parameters does the fish species need?
  • keep in shoals or in pairs?
  • do the fish tend to multiply?
  • is socialization possible?
  • how should the aquarium be set up?
  • what food is needed?
  • what water temperature is needed?

Decide on one type of fish

It is easiest if you decide on a type of fish. You choose one that you particularly like. It is then necessary to select and set up the aquarium accordingly. Now you can go in search of other species of fish, always adapted to your favorite species that you initially chose so that they are similar in setup and water parameters and will also get along well.

Examples of fish stock in different aquariums

Of course, there are different-sized aquariums, all of which are suitable for different types of fish. Starting with the small nano tanks, through the beginner’s aquariums with a few hundred liters, to the very large tanks, which allow a volume of several thousand liters.

The stocking you ultimately decide on is of course not only dependent on the size and layout of your aquarium, but also on your own taste.

Here some examples:

Nano basin

A nano tank is a very small aquarium. Many aquarists do not see the nano tank as a suitable habitat for fish because they are far too small. For this reason, nano tanks are often used as natural tanks to create different landscapes. Often only small shrimp or snails live here. If you still want to use the nano tank for fish, you should opt for the particularly small species.

The different fighting fish, which can be found under the name Betta Splendens, are particularly popular for the Nano. This is kept completely alone because it is not suitable for socializing with other fish species and mainly attacks fish species with colorful tails. It is important to equip the nano aquarium with floating plants when keeping a fighting fish.

In addition, mosquito rasbora or guinea fowl rasbora can also be kept in such a small tank, whereby a cube with at least 60 liters is more suitable for the latter. The mosquito rasboras, on the other hand, feel comfortable in a small group of 7-10 animals in a 30-liter tank. Both types of fish are swarm animals, which should only be kept with several conspecifics. However, these are not only suitable for the nano aquarium, but of course also for larger tanks in which they are often kept in large groups of more than 20 animals.

  • Fighting fish (keep alone urgently);
  • Guinea fowl rasbora (from 60 liters);
  • Mosquito danios (from 30 liters);
  • Killifish (Ringelechtlings and Co);
  • shrimp;
  • snails.

When it comes to nano aquariums, opinions differ. Many fish experts are therefore of the opinion that fish have no place in a nano aquarium, which, however, does not apply to the betta fish mentioned above. Because all shoal fish have the need to move and swim around in schools, which doesn’t work in such a small cube. For this reason, you should refrain from doing this in smaller tanks under 54 liters and also provide the small fish species with a larger habitat. This is especially true if you don’t know at the beginning what size aquarium it should be. Better one size bigger than too small!

The 54-liter aquarium

Even the 54-liter aquarium is much too small for most fish species. With such an aquarium, it is advisable to select the fish species for the different areas in the aquarium. For example, there is enough space on the floor for the cute panda catfish, of which you can buy six or seven because they remain very small and swarm over the substrate to clean it. Furthermore, there would still be room for a few guppies and possibly a pair of dwarf gourami. Add a few snails and you have a wonderful mixture of fish that have enough space to swim.

  • 7 panda catfish for the floor;
  • 5 guppies;
  • a pair of dwarf gouramis;
  • Snails (e.g. snails).

112-liter aquarium

The next most common size is the 112-liter aquarium, which already offers plenty of space to use different fish and also leaves plenty of room to let off steam in terms of decoration. In this aquarium, for example, the floor size is already sufficient to use 2-3 catfish. Here it is advisable to keep one male with two females because males fight for their territory, and the aquarium is then too small for two territories. In this case, however, it is important that you use caves to ensure that the catfish can hide during the day. A root to gnaw off should also not be missing. Now you can, for example, use a swarm of 10-15 neons and a butterfly cichlid, so that the new aquarium becomes a real eye-catcher.

  • 2-3 catfish or a large school of pander catfish;
  • 10-15 neons (blue or black);
  • butterfly cichlid;
  • snails.

200-liter aquarium

The 200-liter aquarium is usually not for beginners, which means that the aquarist should usually be familiar with the fish stock. Here, too, the bottom is already suitable for several antennae catfish, which can also be kept together with pander catfish or metal armored catfish. Guppies, platties, and perch also feel very comfortable in such a tank. A possible population would be 3 armored catfish, 10 metal armored catfish, and a swarm of 20 blood collectors.

  • 2-3 catfish;
  • 15 metal armored catfish;
  • 20 blood collectors or 15-20 guppies with a swarm of neons.

Of course, the fish stockings mentioned above should only be treated as suggestions. Because your taste should not be neglected under any circumstances. However, please make sure that you do not use too many fish, but always give the animals enough space to swim and develop.

What is the correct way to introduce fish?

It is important to let the aquarium run in properly before introducing fish for the first time. This means that in addition to the substrate, the decoration and the plants should also stand for a certain period of time. And the technology must already be broken in. The water parameters should be tested more frequently during the break-in period to ensure that they are stable when the fish are introduced. The break-in period should be at least four complete weeks. This is related to the development of bacteria, which are important for the fish. These must settle in the filter units of the technology. With a long running-in period, the plants also have the opportunity to get strong roots and grow to a sufficient size. For this, it is important not only to let the filter run. The heating and the aquarium lighting must also be switched on urgently.

After purchasing the fish, they should not be placed directly from the bag into the aquarium. If there are no fish in the tank yet, but it is the first stocking, please proceed as follows:

  1. Open the bags containing the fish and place them on the water surface, attach them to the edge of the aquarium and wait 15 minutes. This allows the water in the bag to take on the water temperature of the pool.
  2. Then put half a cup of aquarium water in the bag with the fish so that they can get used to the water. Repeat this process 2 more times, always waiting 10 minutes in between.
  3. Now catch the fish with a landing net from the bags. Never pour the water into your aquarium, but dispose of it afterward. In this way, you play it safe that you do not endanger the water values in your pool.

If it is not the first stock, but additional fish that are to live in an aquarium with existing animals in the future, it is advisable to place them in another aquarium for a quarantine period and only move them after a waiting period of four weeks. In this way, you can prevent the spread of diseases in your already well-functioning tank.

Conclusion – it is better to provide more information than too little

If you do not know exactly whether the fish are suitable for the purpose of stocking the right fish for your aquarium, it is advisable to consult specialist literature. Special aquarium forums on the Internet are also a good place to go for specific questions. However, a pet shop or hardware store that sells fish should not necessarily be believed, because the focus here is usually on selling the fish.

Mary Allen

Written by Mary Allen

Hello, I'm Mary! I've cared for many pet species including dogs, cats, guinea pigs, fish, and bearded dragons. I also have ten pets of my own currently. I've written many topics in this space including how-tos, informational articles, care guides, breed guides, and more.

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