How to set up an aquarium correctly? (Step by step, hints)

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Fishkeeping is a great hobby. It allows you to create your own piece of the underwater world in your aquarium. What should we know before buying a fish?

Setting up an aquarium is an undertaking that must be carefully thought out, planned and divided into stages. We cannot spontaneously enter a pet store, buy aquarium tank, equipment and, most of all, live fish and plants, claiming “it will be fine somehow”. Well, no, it won’t. In this material, I will guide you through the preparation stage for creating an underwater micro world in your home.

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STAGE I: Gathering information

In order to choose the species of fish for our aquarium, we must learn as much as possible about them
In order to choose the species of fish for our aquarium, we must learn as much as possible about them

When the decision to set up an aquarium has been made, we have two ways:

  1. Choosing the species and quantity of fish that we would like to keep and adjusting the size of the aquarium and water parameters to them.
  2. Determining the conditions that we can create for fish and selecting such species that will feel good in them. I recommend this way.

The conditions that I am writing are mainly the space to live for fish (the size of the aquarium) and the parameters of the water – the general hardness and pH. You will learn about other parameters (e.g. carbonate hardness, concentration of nitrates, nitrites, ammonia, phosphates) in the following articles.

We should carefully plan where the aquarium will be placed. It must not be exposed to sunlight, as this may cause algae attack. A place near a heat source (eg a radiator) is also not suitable due to the high chances of overheating the water and “boiling” the fish, especially in the case of small aquariums. The tank will weigh a lot, so it must be stable and on a level surface to minimize the risk of glass breakage and flooding of the flat.

The size of the aquarium depends on our preferences, space, financial resources, etc. However, remember that the larger the aquarium, the easier it is to maintain the biological balance and stable parameters.

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What is water hardness?

The total water hardness (TwO, GH) depends mainly on the amount of dissolved calcium and magnesium ions. It is most often given in German degrees (on), less often in milivalents (mVal) of calcium and magnesium ions per 1 dm3 of water. We measure it with special tests, e.g. by the Zoolek company.

Water hardness scale

1on of total hardness corresponds to the content of 17.8 ppm (parts per million, which describes the concentration, i.e. the number of grams of the substance in 1,000,000 grams or milliliters of solution) CaCO3

1on carbonate hardness = 21.8 ppm HCO3

Depending on the degree of water hardness, we divide into:

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very soft: 0 – 5 on GH
soft: 5 – 10 on GH
medium hard: 10 – 20 on GH
hard: 20 – 30 on GH
very hard: over 30 on GH
In practice, we test it using, for example, easy-to-use droplet tests. The test strips are less accurate.

It can be influenced, lowered or raised, but it is a slightly higher driving school. But about that another time.

Most species of fish can be kept in medium-hard and hard water, but some require soft water and should be provided with it. In the case of reproduction, the carbonate hardness is also important.

What is the pH of the water?

The pH value is a measure of the pH of the water. This parameter may be subject to daily fluctuations due to such life processes of organisms as CO2 assimilation (plants take up carbon dioxide for photosynthesis) and respiration.

The pH of the water can be measured very accurately with a pH meter, but it is quite an expensive device. We can less accurately determine the pH using color indicators in the form of solutions (e.g. bromothymol blue in the range of pH 6.2 – 7.6, methyl red in the range of pH 4.2 – 6.3. This method, however, is not very practical and requires practice. Bar indicators available in pet stores have the advantage that, apart from pH, they also measure other water parameters, e.g. water hardness, nitrites, nitrates, etc. for pH measurement (cellulose, litmus or other soaked in dye).

The pH scale ranges from 0 to 14, with 0 being the strongest acid, 7 being neutral, and 14 being the strongest base.

Most fish and aquarium plants do well at a pH of around 7.

How to choose fish for our aquarium?

Having these data on water, we can proceed to the selection of species that will feel good in the conditions that we can create for them.

There are also a few rules here:

  • we avoid the so-called “Fish soup”, ie keeping together species of fish that require different conditions. If we care about the variety of colors, I recommend the viviparous species (gladiolus, mollies, guppies, varieties), which have a lot of color forms, and are easy to breed and tolerate a wide range of water conditions;
  • shoal fish (e.g. neon, cuirass, razbory, danios) must be kept in groups. In addition, we try to create the largest possible groups from the smallest number of species;
    we try to combine species that reach similar sizes. This way we will avoid the risk of eating smaller fish by larger ones;
  • fish that like to nibble their fins (e.g. barbels) should not be combined in one aquarium with those with long fins (veiled zebrafish, goldfish, angelfish, etc.)
    for small aquariums, we do not buy fish that reach large sizes (e.g. angelfish, goldfish, catfish, sharks, etc.). In cramped conditions, the backbone of fish stops growing, but the internal organs continue to grow and such a fish is literally torn from the inside;
  • do not introduce too many fish into the aquarium (we do not allow overfilling). A mythical conversion factor has been circulating for a very long time among beginner aquarists, which allegedly allows to calculate how many fish of a given size will “fit” in an aquarium of a certain size. Converting the length of a fish to liters of water in a tank is absurd. Why? You can read about it in the next article.

There are tons of books and websites where we can find descriptions and requirements for our chosen fish species. It is best to look for information in various sources so that you can compare the obtained messages and verify them. It is also very important to verify the acquired knowledge with experienced aquarists, whose opinions can be obtained through, for example, specialized online forums.

Being aware of the needs of our pupils, we will be able to take care of them as best we can, and in return we will have a chance to enjoy a healthy and beautiful aquarium.

STAGE II: Completing the equipment

You will need: an aquarium, a foam mat under it, a cover with lighting, a filter, a heater, a thermometer, a substrate, plants and decorations
You will need: an aquarium, a foam mat under it, a cover with lighting, a filter, a heater, a thermometer, a substrate, plants and decorations

Once we know how big an aquarium we can afford, we proceed to complete the equipment. What is needed to set up an aquarium?

  • an aquarium and a foam mat or pad,
  • cover and lighting,
  • filter,
  • heater,
  • thermometer,
  • an aerator (usually not needed in the aquarium, especially with a lot of plants),
  • extension cords and splitters,
  • subsoil,
  • plants, if we choose them (alive! artificial plants can hurt fish),
  • a net for catching fish,
  • stones, roots or other decorations.


You can often find ready-made aquarium sets (e.g. from Aquael or Diversa) that already contain basic equipment.


We can buy an aquarium ready-made or order it from a glazier, especially if we plan a tank of unusual sizes, and such an aquarium will in most cases be better than ready-made from the store.


Stand or mat

There should be a special pad or foam mat under the aquarium, designed specifically for this purpose (to be bought at an aquarium store or online), but the foam used to arrange the panels, polystyrene or a foam pad will also work well. Such an undercoat is designed to level any unevenness and prevent stresses acting on the bottom of the tank.

Cover and lighting

The cover should fit exactly to the top edges of the aquarium. Ready-made covers are available in stores, most often with an already mounted light source.

If we decided to use an open tank (without a cover), the lighting installation should be planned so that it does not come into direct contact with water. Remember that from time to time we will have to put our hands into the aquarium, so there must be easy access to it. In such aquariums, lighting beams are used, leaning against the aquarium glass or suspended above it.

Two types of fluorescent lamps are most often used as lighting: T8 (26 mm in diameter) and T5 (16 mm in diameter). Lamps with LED diodes are also gaining more and more popularity.


The filter in the aquarium is designed not only to clean the water of visible mechanical dirt. The filter media is also a breeding ground for beneficial bacteria that purify the water biologically.

How to choose a filter for an aquarium?

When choosing a filter, we must have in mind that it is better to have too much filtration than insufficient. Each filter has a specific range of aquarium capacity, which will be provided with adequate filtration. Nevertheless, it is better to choose based on this lower value, i.e. if you intend to have an aquarium with a capacity of 60 l, you should choose a filter for aquariums 60-100 l, not up to 20-60 l.

Types of filters in the aquarium

internal – mainly used in smaller tanks. However, they take up a lot of space and have very limited space for filter beds. In larger aquariums they are used as mechanical filters, and the role of biological and chemical filters is played by bucket filters;

external cascade – most convenient in open aquariums, due to the fact that they are hung on the edge of the aquarium. Have more space for filter media;

external canister, also called bucket type – They take up little space in the tank, because filtration takes place in a special container that is connected to the aquarium with hoses. It can be hidden in a cupboard under the aquarium. In addition, this type of filters has the greatest filtration capabilities, not only due to the number of deposits, but also the fact that we can use various types of them (basic: sponges, ceramics, volcanic lava with high porosity, filter wool; for special tasks: activated carbon , peat, zeolite, etc.). Desirable for medium and large aquariums.


Like filters, specific models of heaters are designed for aquariums of appropriate size. The heater for our aquarium should have a thermostat with the possibility of temperature regulation.

We have several types of heaters:

the most common: glass tubes with a heating spiral inside;

ceramic – much more durable, especially recommended for aquaterrariums with terrestrial turtles and crabs (e.g. EASYHEATER by Aquael)

flow – mounted on the hose leading out the water from the bucket filter to the aquarium (e.g. ETH by Hydor), intended for aquariums over 100 l.


Various types of thermometers are available on the market: from strips stuck on the outside of the aquarium, through classic glass alcohol thermometers, attached with a suction cup, to electronic devices. Electronic devices are the most expensive, but they are also the most precise. Strip thermometers are sometimes difficult to be read.


The substrate should not change the water parameters, especially it can not increase its hardness and pH. The exceptions are aquariums for species that require hard and alkaline water, such as fish from lakes Tanganyika and Malawi. It is best to choose natural quartz sand and gravel, with a grain diameter of approx. 2 – 5 mm (optimal for plants). We avoid dolomite and basalt, which make the water harder, as well as artificially colored pebbles.

We can buy natural sands and gravels in pet stores, but those from gravel pits, ore warehouses, DIY stores are also suitable. The amount of substrate needed for our aquarium can be calculated here.


Plants, like fish, have different requirements for growing conditions. They mainly concern lighting and the content of various elements in the water, and even the abundance and thickness of the substrate particles. In addition, they grow in different ways: we have stem plants that grow tall, rosette plants that take up space mainly to the sides, and grass and lawn plants that cover larger areas of the ground. Therefore, when buying, apart from aesthetic reasons, we must also be guided by the needs of the plants we choose and the nature of their growth. There is no need to overdo the number of plants, because they will grow. We allocate about 10 cm square of space for each species, thus calculating how many plants we can plant.


For decoration, we can use stones that will not change the water parameters. We avoid all kinds of limestone, unless we plan an aquarium with fish from the African lakes of Tanganyika or Malawi. The safest are fragments of volcanic lava or pieces of lignite. The use of pebbles is also a good solution.

Roots with fanciful shapes are available in stores, but we can also try to prepare them on our own, but it is time-consuming, because such wood must be seasoned and properly dried.

STAGE III: Preparations

Place a foam mat or pad between the top of the aquarium and the glass
Place a foam mat or pad between the top of the aquarium and the glass

When we know where the aquarium will be located, we have bought equipment and everything we need, we can get to work.

Preparation of roots and stones

Roots require preparation by boiling them in water with non-iodized rock salt (e.g. salt for cucumbers; available in grocery stores), and then in water without salt. The wood must be completely covered by water, so we can also boil stones that will help us add weight to the wooden decorations. After boiling, pour clean water again and set aside. This process should be carried out as soon as possible, e.g. on the day of purchase. If the wood is not sufficiently soaked, it can tend to float. The thicker it is, the longer it will take to sink. During the soaking period, we replace the water with clean water every day.

Water purification

At the beginning, we must remember not to pour water straight from the tap into the aquarium, because the chlorine contained in it can kill beneficial bacteria and negatively affect the plants. Therefore, before flooding the aquarium, pour water into buckets or other larger open containers, which we leave for 24 hours to allow the chlorine to evaporate. Water prepared in this way does not require treatment with preparations that remove this element from the water.

Preparation of the aquarium

In order to enjoy a healthy aquarium, at this stage we must realize how important it is to follow the rules of hygiene. Hands should be washed thoroughly, preferably with disinfectants, both before and after handling the aquarium.

We clean the aquarium with a clean sponge or cloth, only water. For any more difficult stains, we can use vinegar or citric acid, and then rinse well with water. Do not use any detergents as their residues may be toxic to any living creatures in the aquarium.

After drying, place it in a place chosen by us, remembering about a foam pad or mat.

Substrate preparation

The ground should have a clear slope, it should be lower in front than in the back. This will add depth to the aquarium and make it easier to clean up debris. Sometimes we need to install some decorations at this stage
The ground should have a clear slope, it should be lower in front than in the back. This will add depth to the aquarium and make it easier to clean up debris. Sometimes we need to install some decorations at this stage

Before placing in the aquarium, thoroughly rinse the sand or gravel until the poured water is clear. Place the substrate in the tank in such a way that a slope is formed, at the front lower (minimum 3 cm), at the back higher (minimum 6 cm), additionally, you can make a slight slant so that the lowest point of the substrate is at one of the angles. This will allow contaminants to flow down to one place, from where it will be more convenient for us to remove them with a hose or a desilter.

Installation of equipment

After leveling the ground and arranging larger decorations, install the filter and the heater
After leveling the ground and arranging larger decorations, install the filter and the heater

Time to get your hardware installed. For aesthetic reasons, the filter is placed at the rear end of the side window. Such a location will enable good water circulation in the aquarium and the possibility of covering the technical element with plants or other decorations.

The heater, to be able to properly and effectively fulfill its function, should be located in a place with good water flow. On the other hand, attach the thermometer as far as possible from the heater, but also where there is significant water movement – only then will the readings be reliable.

Laying decorations and pouring water

Pouring water in a thin stream over the plate will help to avoid disturbing the substrate and damaging the arrangement
Pouring water in a thin stream over the plate will help to avoid disturbing the substrate and damaging the arrangement

Now is a good time to arrange the wood, stones and decorations. If the wood is still flowing out, we can temporarily weight it down with stones or otherwise fix it in place.

We must pour the water carefully so as not to disturb the arrangement of the substrate. For this purpose, we use a jug or a thin tube, under the outlet of which we put a plate. This will prevent the formation of pits and the disturbance of sand or gravel. We fill the aquarium up to 1/3 of its height to make it more convenient for us to plant the plants.

Preparation of plants for planting

Before planting, disinfect the plants in a slightly pink solution of potassium permanganate
Before planting, disinfect the plants in a slightly pink solution of potassium permanganate

Plants should be prepared before planting. If we bought plants in baskets, take them out and carefully remove the mineral wool. In the case of plants grown in vitro, get rid of the gel from between the roots and rinse with water. Using sharp scissors, remove damaged leaves and dark-colored roots that may indicate their rotting. Healthy roots are more or less white in color.

Then the seedlings should be disinfected by soaking for 5-10 minutes in a solution of potassium permanganate, which we can buy cheaply at any pharmacy. A few small crystals (3-4) for a few liters of water are enough to obtain an effective solution; we should get a slightly pink color. This agent is very dirty, so all manipulation with it should be carried out over the bathtub or washbasin (preferably ceramic, because brown stains from potassium permanganate come off extremely hard from plastics) and wear latex gloves.

Thanks to this treatment, we will get rid of all unwanted creatures and most of the algae.

Planting plants

Plants are planted with tweezers or by making a hole with your finger. Regardless of the technique, we must be careful not to tuck the roots
Plants are planted with tweezers or by making a hole with your finger. Regardless of the technique, we must be careful not to tuck the roots

Stem and larger plants are planted at the rear glass of the aquarium and up to the middle half of the side, medium height and rosette plants in front of them, and leave the front without plants or place low lawn plants.

The technique of planting plants is important: make a hole in the substrate (e.g. with a finger) and then place the roots of the plant in it so that they do not tuck up. We smooth the sand around and we can start the next piece. As part of fertilization, we can place a clay-peat ball (e.g. from JBL) under the seedling.

If the water is dirty, we can gently suck it up with a hose
If the water is dirty, we can gently suck it up with a hose

Starting the hardware

After planting the plants, the water will probably be cloudy, so you can drain it from the aquarium with a hose, and then add clean water using the previously described technique. We must remember that the hose outlet outside the aquarium should be well below the water level.

If we lack treated water, we do not have to fill the entire aquarium immediately, it is important to cover the plants. Below the pane, there must also be a filter that we run. If we lack treated water, we can refill the buckets and refill the aquarium the next day.

The thermostat of the heater, which must also be almost completely underwater, is set at 23-24*C, which is sufficient for most aquarium plants. In this way, we save electricity as long as there are no fish in the aquarium.

We assemble the lighting and the cover. We turn on the light only on the second day, following the scheme: in the first week after flooding, we only shine 4-5 hours a day, then every week we increase the exposure time by one hour, until we reach 10 hours a day. In this way, we minimize the risk of algae infestation.

To adjust the length of the day in the aquarium, a timer is useful, on which we can precisely set the hours of switching on and off the lighting.

STAGE IV: Maturing the aquarium

An aquarium filled with water has to mature for about a month before we can let the fish in
An aquarium filled with water has to mature for about a month before we can let the fish in

In order to admit the fish, the aquarium must be mature, or at least stable, which is largely due to filtration. In the aquarium, apart from mechanical filtration, which is mainly provided by sponges in the filter, we also deal with biological filtration, for which various bacteria are responsible. They convert the waste products of fish into substances available for use by plants. This process is called the nitrogen cycle.

For an aquarium to mature, it takes time for the beneficial bacteria to multiply. To this end, we sprinkle some fish food into a newly set up aquarium, and then for about a month we do nothing in the aquarium except weekly extending the hours of the light on.

After this time, we change about 1/4 of the water volume and we can get ready to buy fish.

STAGE V: Purchase of fish and quarantine

The fish are transported in special bags
The fish are transported in special bags

To enjoy a healthy aquarium, we must choose the right fish and properly acclimatize and quarantine. Without it, an adventure with aquaristics can become a torment, effectively discouraging this wonderful hobby.

Why is proper quarantine so important?

Each organism produces resistance to microorganisms in its environment. If you mix water from multiple aquariums, the fish will be surrounded by microorganisms that they have not dealt with before. The stress of purchasing and shipping lowers immunity, which can lead to disease and death. These effects can occur right after the purchase, but also even two or three weeks later, when nobody thinks it is due to improper acclimatization and quarantine. That is why they are so important.

Where is the best place to buy fish?

We buy fish only from proven breeders. Before asking to catch fish, we must observe the aquarium: are the fish swimming normally? Are there white dots, abrasions, cavities, or other changes to their skin or fins? If we observe any abnormal symptoms in any of the fish, we do not buy fish from that aquarium.

Transport of fish

Fish for transport should be in bags with water. In jars and other vessels, fish are highly exposed to mechanical injuries caused by the movement of the container. The pouches largely reduce these negative physical factors.

Transport home should be as short as possible due to the limited amount of oxygen and the accumulation of harmful metabolic products in the water in the bag. The fish should not be exposed to rapid temperature fluctuations (especially important in winter). They are cold-blooded animals, which means that the temperature of their organisms is closely related to the ambient temperature. If the temperature is too low or too high, they will simply die. Therefore, a good solution in winter is to hide the bag of fish next to the body under the jacket.

Acclimatization of fish

The acclimatization tank must be adapted to the size and number of fish.
The acclimatization tank must be adapted to the size and number of fish.

At home, in order to equalize the temperatures, place the closed bag in the acclimatization tank (which may be a bucket or other large container) for about 20-30 minutes with a small amount of water prepared in advance and at a temperature appropriate for the given fish.

Now it’s time to open the fish bags. We do this slowly and carefully to avoid sudden pressure changes. Then we gently pour the fish into the acclimatization tank. WATER FROM BAGS NEVER BE POURED INTO AQUARIUM! After about an hour, slowly add water from the aquarium and pour out the water from the bucket. By stretching this process for a few hours, we give the fish time to get used to the new water parameters, thus minimizing stress. A convenient method for slow water changes is to use a thin tube, e.g. a silicone tube. We gently aerate the water in the container.

Quarantine aquarium

Quarantine should be carried out in an aquarium adapted to the size of the stocking and mature, i.e. one with a closed nitrogen cycle and stable parameters. We can carry it out in the target aquarium, if there were no fish in it before. If we want to increase the population, we quarantine in another aquarium with efficient filtration and decor similar to the natural environment of the species: do not be afraid to plant a few simple plants, twigs and stones for fish that live in such conditions.

Quarantine should last a minimum of two weeks. This is the time when fish get used to the new biological environment. We also need it to observe new pupils: do they behave and eat properly, do not show symptoms, etc.

Transfer the fish with the landing net. For the next few days, after letting it into the quarantine tank, change approx. 10-15% of the water volume in it every day (to stand still and at a temperature similar to that in the aquarium), add non-iodized rock salt in the amount of 0.05-0.1 g per each liter of the changed water. Rapid changes of 50% each result in fluctuations in parameters, which negatively affects the fish and other organisms in the aquarium. We limit lighting.

We do not feed for the first two days. Fish that are stressed after transport have reduced immunity, do not eat or digest properly because they are not used to the new food. Uneaten food stays on the bottom and spoils the water, while poorly digested food can remain in the intestine, leading to its clogging and the multiplication of undesirable microorganisms.

Medicinal preparations must not be used hastily! If it is necessary to use them, we should adjust them to the symptoms and causes that cause them.

STAGE VI: Further care for the aquarium

Caring for an aquarium is really nothing difficult. It mainly comes down to feeding the fish and water changes. From time to time, we should trim the plants that require it and desludge the substrate.

Feeding the goldfish

You should feed your fish in the morning or before noon, in small portions that will be eaten within minutes. We do not give food at night, because then it is less digested and lying in the intestine is an excellent medium for microorganisms. This does not apply to species that forage at night (e.g. catfish).

Water changes

Once a week, we change approx. 30% of the water volume with the one prepared a day earlier, with a temperature similar to that in the aquarium. By the way, we can pull off the dirt accumulating in the lowering of the substrate with a hose or a desilter, which we have prepared for this purpose at the stage of arranging the aquarium.

Pruning plants

Mainly stem plants require pruning. We shorten them to a few centimeters so that they can release more side shoots and thicken. The cut off tops can be planted next to it, thanks to which we will get an even more compact clump. For a similar purpose, we also trim lawn plants, but those just above the ground. We also use scissors to remove dead, damaged or heavily clogged leaves.

Glass cleaning

Once in a while, when the situation requires it, we clean the windows from the inside during the water change. How to remove algae from windows? For this purpose, sponges, special magnetic cleaners or razor blades are used. You can also use an old plastic card (e.g. credit card), but after removing the chip. Personally, I have been using the latter method for years.

Setting up an aquarium is a very laborious process, but if we prepare everything carefully, we will save ourselves problems and additional work in the future.

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About this category

Animal at home is a project derived from the Polish portal dedicated to domestic pets, which I run. This blog category features the best articles I have created with pet experts. Together, we help educate their current and future owners.

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Jakub Markiewicz
Jakub Markiewicz
Hi, I am the author of the blog and series of thematic portals since 2013. I have nearly 15 years of experience in working in the media, marketing, public relations and IT. If you are interested in cooperation, you would like me to write about something or test a product - let me know.