Aquarium Water and Everything About It

Many novice aquarists focus on choosing fish, plants, and beautiful equipment, while water is just something to pour from the tap. This is a major mistake. Water is not just a habitat; it is a complex, living world, on whose condition the health of all aquarium inhabitants directly depends.

Tap water often contains chlorine, heavy metals, and other substances that are safe for us but dangerous for fish. Therefore, it is necessary to let it stand or use special conditioners. But this is only the first step. It is important to understand that water has its own “characteristics,” such as hardness and acidity, which must be suitable for specific species of fish and plants.

Maintaining proper water quality is the basis for success in aquarium keeping. Regular water changes, monitoring cleanliness and parameters, and using filters are not routine tasks, but rather caring for an entire ecosystem in your home. In this article, we will explain in simple terms how to turn ordinary water into the perfect home for your underwater pets.

Why you need to change the water in your aquarium

Cleanliness behind the glass walls is an essential condition for a home biotope. Water contains substances necessary for life. Fish not only breathe dissolved oxygen, they also obtain beneficial microelements from the liquid. To ensure a constant supply of fresh compounds, the water must be refreshed regularly.

Basic rules for changing water

• You cannot drain the entire aquarium;
• Do not change more than 30% of the total volume in large aquariums.
• Do not change more than 15% of the volume in aquariums up to 30 liters.
• Not only should you change the water, but you should also clean the substrate at least once a month.
• Water preparation is an important step. Home testing is necessary, especially at first, when you have no experience and do not know how often to change the water.

Let's take a closer look at each point.

Water change technique: don't drain it all!

A huge number of novice aquarists still perform an unnecessary and energy-consuming procedure: they completely drain and refill the water, transferring the fish to a jar for several days. By the way, those who are hesitant to get an aquarium with fish often say: “Oh, you have to change the water, it's so difficult, I'm afraid.”

Under no circumstances should you completely drain the water in the aquarium! No aquarium fish requires this from its owner! The only reason you would have to do this is if there is an emergency in the aquarium. For example, a serious incurable infectious disease that has killed all the inhabitants. Relatively mild infections such as ichthyophthiriasis, which can be treated with antibiotics, do not require a complete replacement and restart of the aquarium.

How can you keep the tank clean? With regular water changes and periodic cleaning of the bottom.

Water is a harmless substance that can poison the lives of your pets. It is the familiar habitat of fish.

Why you can't completely drain the water:

• Any body of water is a complex biological system. By completely draining the water, scrubbing the walls until they shine, and boiling the soil, you are not only disrupting the integrity of this system, but destroying it.
• Fish that have to be caught out of the water experience terrible stress, which affects their lifespan.
• As a result of a complete water change, the parameters change dramatically: hardness, acidity, and even the content of nitrites and nitrates. Any sudden changes are detrimental to fish; the quality of the environment must always be improved gradually, even if the water is very poor.
• As a rule, aquarists engaged in such a thankless task do not have a special “holding tank” and transfer the fish to a jar or bucket. Even one day in cramped and frightening conditions can kill the most vulnerable fish and shorten the life of seasoned fighters.

Starting an aquarium: rules

• If the aquarium is new and you are filling it with water for the first time, you will have to wait 8-10 days. Firstly, this is the easiest way to prepare the water. Secondly, you will be able to check how well the seams are sealed and whether there are any leaks. You can fill it with the entire volume at once or gradually increase the level over several days.
• When starting the aquarium for the first time, you can place an object in it or add 10-15% of the volume with water from another successful and healthy aquarium. You can put an old sponge in the filter or carefully transfer two or three large stones. The bacteria contained on the objects will start the processes and prepare the water for new inhabitants more quickly.
• After 5-7 days, perform tests to determine whether the water is ready to accept new inhabitants.

The water in an aquarium is not just a transparent liquid, but an entire environment on which the health of fish, plants, and the entire ecosystem depends. It must be clean, but not sterilized, with the appropriate hardness and acidity level, and chlorine and other harmful substances from the tap must be removed. Simple in appearance, it requires attention: regular changes, monitoring of parameters, and proper water preparation are the key to healthy fish and green plants. A good aquarium does not start with rocks or fish, but with the right water.

How to change the water in an aquarium

The ideal aquarium cleaning routine is as follows:

• Clean the walls from the inside with a soft sponge.
• Rinse the filter.
• Clean the substrate with a special siphon, draining up to 20% of the total volume.
• Adding fresh water.

How often should you change the water in your aquarium?

The substrate should be cleaned 1-2 times a month. It is recommended to refresh the water 2-3 times a month. It is not necessary to combine these two tasks. You can drain some of the water with a clean tool (hose or cup) directly from the surface and add fresh water.

Strangely enough, a large aquarium requires less effort from the owner than a small one. In aquariums up to 50 liters, all processes occur faster, which means that the water spoils faster and the soil gets dirty.

An important rule: do not change the water too often. Daily water changes are only good in special circumstances, such as when caring for the fry of certain fish. The less often the balance is disturbed, the better.

What kind of water to pour into a fish tank

Let's say right away what liquid is NOT suitable under any circumstances: boiled water. In terms of its usefulness for fish, it can be equated with beverages such as tea or soda. It does not contain any beneficial microorganisms or “living components,” but it may contain substances that are harmful to the aquarium. It has a high softness index and can be added in small amounts.

Another risky option for changing the water is well water, lake water, or river water. There is a high risk of introducing viruses, harmful bacteria, and chemical compounds into the aquarium.

In extreme cases, the following can be used for replacement:

• Filtered water (like tap water, it needs to be settled to remove chlorine compounds);
• Bottled water (you need to test it for hardness beforehand. In general, store-bought water is a fairly expensive option, although it is quite suitable);
• Distilled water (some fish, such as neon tetras, need it to stimulate spawning, but in general it is only suitable for diluting tap water);
• Rainwater, melt water (similar in composition to distillate, too clean, devoid of life, and may also contain impurities: harmful elements and heavy metals).

Strangely enough, tap water is considered to be the most favorable in terms of composition. It has a more or less stable composition and is easy to treat (it can be settled or other tricks can be used).

How long to let aquarium water settle

• Tap water – 3-7 days;
• Filtered water – 3-7 days;
• Bottled water – no settling required;
• Rainwater, river water, melt water – 5-6 days;

Settling helps to reduce chlorine levels to safe values. In addition, during the settling period, the water reaches room temperature. If the fish like warm water and the heater is constantly running, there is no need to heat the settled water separately: the recommended volume for replacement will not significantly affect the temperature of the entire biotope, and the heater will quickly bring this parameter back to normal.

Water parameters

How many days to let the water settle depends on the characteristics of the specific liquid. They can even differ in different parts of the same city! Ideally, it is best to take samples and do tests before each water change. But in practice, few people do this (only if the fish are particularly valuable and demanding, such as discus fish). It is enough to do the testing the first time to determine the parameters:

• Chlorine content;
• Hardness;
• Acidity (pH level).

There are special test strips or portable devices available for purchase that can help you determine how far the water parameters are from the desired ones in 1-2 minutes.

A few tips for preparing water:

• To remove chlorine, let the water settle.
• Water that is too hard can be softened by adding distilled or boiled water.
• To make it harder if it is too soft, you can put natural coral, shells, or any other limestone in the bucket during settling.
• Acidity can be adjusted with special additives sold at pet stores.

Tap water usually does not require any special preparation, as its values are within the average range.

How to let water settle

For best results, pour the water and let it settle in a place where there is no dirt. It is better not to cover it.

Set aside a special clean container in which only aquarium water will be stored. Make sure that no one washes their hands or the floor in this bucket. Even a small amount of soap or detergent can make the water toxic to fish! Remember: aquarium equipment must be clean, and this also applies to buckets (bottles) for settling water.

There are special aquarium conditioners available for purchase. They help prepare tap water, instantly removing chlorine and other compounds. In this case, no settling is required: just pour the water into a clean container and add the conditioner. You only need to monitor the temperature.

How to determine what kind of water is suitable for fish

Usually, the description of each aquarium fish includes the characteristics of the water in the biotope in which it lives in nature. These should be used as a guide. The lower and upper limits are given.

How to know when it's time to change the water

Can't remember how many days have passed since the last water change? Take a closer look at the aquarium:

• If there is a film on the walls;
• If the water is not clear and clean enough;
• If there is a lot of substrate on the surface of the soil;

This means that you need to not only change the water, but also give the aquarium a thorough cleaning.

Get into the habit of testing your aquarium water once a week: if any parameters move into the danger zone, it's time to change the water!

As you can see, the water in an aquarium is not just H₂O that you can pour from the tap. It is a whole living environment, the basis for the health of your fish and plants. Absolutely everything depends on its quality: how bright the inhabitants will look, how active they will be, and even how long they will live.

Therefore, don't be afraid to pay enough attention to the water. Regular tests, proper preparation before filling, and timely replacement of part of the water are not rocket science, but a habit that quickly becomes part of your care routine. Modern conditioners and affordable tests make this task much easier.

The main thing to remember is that stability is more important than perfect numbers. Sudden changes in parameters are much more dangerous than conditionally “imperfect” but constant water. Observe your pets, they will always be the first to signal if something is wrong.

Ultimately, understanding and controlling the water is the key to a beautiful, thriving aquarium. When this balance is found, care ceases to be a routine and becomes a real pleasure, and your underwater world will delight you for many years to come.