Aquarium Water Treatment Guide For Freshwater and Saltewater

Properly aquarium water treatment is an important component when breeding fish. Even a slight deviation from the norm can result in dangerous consequences for fish or algae.

Therefore, compliance with the basic rules and maintaining the level of indicators in the norm is the main component of the health of underwater inhabitants.

aquarium water treatment guide

aquarium water treatment Fundamental rules

When preparing, it is important to consider the components:

  • solid – settle at the bottom of the container;
  • gaseous – volatilize;
  • liquid (the most rare) – remains in the water.

Water can be used only after a series of procedures:

  • cleaning (by settling or using an air conditioner);
  • settlement of indicators in accordance with the norms;
  • mineralization.

Advice! You can find out the exact indicator using test strips, which are sold at any pet store.

aquarium water treatment products

In order for the water to meet the necessary parameters suitable for the life of fish, various aquarium water treatment products are added to it to improve the quality:

  1. baking soda – to lower the level of acidity;
  2. peat, wood (except oak and species with a high resin content) – to increase acidity;
  3. chalk, limestone – to increase rigidity;
  4. to reduce stiffness:
  5. boiling – add 2/3 of the cooled boiled water to the aquarium;
  6. dilution with meltwater – possible only in ecologically clean areas;
  7. adding soft water – distilled water is suitable for this;
  8. adding ice – freeze the water halfway, then add ice (previously melted) to the aquarium;
  9. water softening capsules – sold at pet stores;
  10. planting plants – algae reduce stiffness;
  11. sodium thiosulfate – powder for purifying water from chlorine and ammonia, added in a ratio of 1 g / 10 l;
  12. cleaning filters – to remove most chemical compounds.

What do water parameters depend on?

The amount of certain substances in H2O directly affects its performance:

  • smell – depends on the amount of bleach and the quality of wastewater treatment;
  • color – a yellowish tint indicates a large amount of organic impurities;
  • transparency – turbidity of water comes from a high level of solid chemical impurities;
  • acidity – indicates the level of hydroxide, acids, and salts;
  • hardness – depends on the amount of calcium, magnesium, and heavy metals;
  • temperature – associated with the reproduction of bacteria and protozoa;
  • gases – determines the presence of oxygen, hydrogen sulfide, and carbon dioxide.

Step-by-step aquarium water treatment at home

Each type of water has its own optimal parameters.

Types of water for aquarium water

what is the best water to use in a fish tank

Tap water for aquarium

It can only be used after standing.


  • budget and convenient option;
  • microorganisms live in it.


  • increased rigidity;
  • the possibility of ingestion of pathogenic bacteria is not ruled out.

boiled for aquarium

Suitable only for those fish that have lived in boiled water since birth.

Pros: no harmful microorganisms and bacteria.


  • when boiling, not only harmful, but also useful micro-objects are killed;
  • for large aquariums, you will need to boil water repeatedly;
  • hardness below normal.

filtered for aquarium

It is considered “dead” water and is strikingly different from the natural habitat of fish.

Also needs to be defended.

Pros: no harmful metals and impurities.

Cons: lack of useful trace elements.

Attention! Water that has been passed through a filter enriched with silver or with an antibacterial effect must not be used for aquariums.

bottled for aquarium

Not suitable for all types of fish, can be dangerous for shellfish.


  • lack of chlorine;
  • does not require upholding.


  • non-compliance with the required level of rigidity;
  • high price.

distilled for aquarium

It is not used to fill the aquarium in its pure form, because it is absolutely sterile and does not have the necessary connections. Suitable for diluting extremely hard water.

rain for aquarium

Similar to distilled, the complete absence of trace elements. Suitable for reducing stiffness, but after preliminary analysis, because may contain harmful acids that kill fish.

From natural sources

Such water can be dangerous for domesticated fish. Therefore, before filling the aquarium from the nearest river, a water analysis should be done.

Time aquarium water takes to settle

How long does aquarium water take to settle:

  1. settling time at least 2 days;
  2. suitable container – glass, clean, which did not contain chemicals (an ordinary jar will do);
  3. lid – the container must not be closed so as not to change the level of oxygen, it is enough to cover it with gauze to avoid dust or dirt.

Important! When pouring prepared water into the aquarium, you should make sure that there is no sediment at the bottom of the jar. These are solid impurities that should not end up in a fish dwelling. If this is found, water should be poured very carefully so that the sediment does not enter the tank.

Some breeders prefer to defend the water directly in the aquarium. This option is not entirely appropriate because of the possible sediment. However, to clean the new tank, it should be filled with water for a few days and then drained. In such an environment, fish cannot be launched.

After that, settled water is collected in a new, cleaned aquarium, which should stand for another week. Only now the environment becomes suitable for fish to live in it.

keep water level in aquarium

The water level depends on:

  • the presence of floating plants – if the water level is too high, they can get burned due to the lighting lamp, the distance should be at least 8 cm;
  • the presence of algae growing on the surface – they need a sufficient amount of air;
  • the presence of snails – if the water level is too high, mollusks can crawl out of the aquarium;
  • a high level can reduce the efficiency of the lighting lamp;
  • in the presence of special fans in the summer, the water evaporates faster, so the level should be slightly higher than usual;
  • in the presence of heaters and filters, care must be taken that the level does not drop much, otherwise the devices may break.

The level also depends on the type of fish:

  1. Ancistrus – two or three individuals can get along in an 80-liter tank;
  2. guppy – suitable for an aquarium of any size with a high water level;
  3. marble gourami – at least 80 liters;
  4. goldfish – a wide aquarium of at least 80 liters per individual;
  5. lalius – 10 liters per fish;
  6. macropod – a 20-liter tank for one individual, be sure to cover it with a lid;
  7. Velifera mollies – a tank of at least 50 liters;
  8. neon – a medium-sized aquarium;
  9. cockerel – a tank of different sizes, depending on the total number of fish.

temperature of water in aquarium

The appropriate temperature depends on the type of fish living there:

  • heat-loving individuals cannot live in the water below 18 ° C;
  • cold-loving ones withstand temperatures below 14 ° C.

Important! Fish that prefer different climates should not be kept in the same aquarium.

28°C is the ideal temperature to start the breeding season. However, if the temperature rises to 35°C or more, the fish may die.

A heater and a fan are used to control the temperature.

Treatment of rigidity of water for aquarium

The required water hardness depends on the inhabitants of the aquarium.

Crustaceans and mollusks require increased rigidity to maintain their shell strength, while some fish and plants, on the contrary, need soft water.

Rigidity is measured in degrees (0 is soft, 33 is hard), so most breeders prefer an average value of 5-15 degrees.

To increase the rigidity of aquarium water:

  1. a piece of chalk,
  2. shells,
  3. limestone.

To reduce the rigidity of aquarium water:

  • boiled
  • melt,
  • distilled
  • filtered water
  • special capsules
  • planted hornwort and elodea.

Treatment of Acidity of aquarium water

Depends on the inhabitants of the aquarium. The pH ranges from 0 (more alkaline water) to 14 (more acidic) but most fish prefer a medium pH of 7.

On a note! In the morning, the pH is usually higher, and in the evening – vice versa.

Soda will help to lower the acidity, peat will help to increase it.

Treatment of Gaseous in aquarium water

The most important gaseous constituent of water is oxygen. All fish need it. The optimal indicator is 7 mg / l. You can find out the exact amount using special testers, sold in pet stores.
The inspection procedure should be carried out regularly in a densely populated aquarium, or if the fish have begun to rise to the surface too often to take a breath of air.

Algae help to increase the level of vital gas, but at night they themselves need air, thereby depriving living creatures of oxygen.

Therefore, a surer way to increase the level is artificial aeration (moving water layers):

  • Compressor – it should be installed next to the heater to avoid sudden changes in water temperature. Among the shortcomings is increased noise.
  • An oxidizer is a stone for aeration. Works without electricity and is completely silent. Of the minuses – less powerful than a compressor and not as durable.
  • Pumps – a filter suitable for small tanks. In addition to aeration, it also purifies water.

Attention! Another equally important gas, especially for plants, is carbon dioxide. The norm of CO2 depends on the hardness of the water, on average it varies from 10 to 25 mg / l.

You can optimize the level with:

  1. cylinders – a specialized system of a reducer and a tube;
  2. mash – a mixture of yeast, water, and sugar;
  3. carbonated water – quickly fills the water with carbon dioxide, but requires frequent refilling (20 ml per 10 liters is usually enough).

How to treat water for aquarium faster?

Since settling is a lengthy procedure, it is possible to water treatment many times faster with the help of specialized water conditioners.

Reference! This specialized tool is absolutely harmless, but it should only be used in accordance with the instructions, otherwise the fish may die.

Pros of water conditioners:

  1. chlorine removal;
  2. antibacterial effect;
  3. normalization of water transparency;
  4. protection against fungi and the appearance of snails;
  5. normalization of pH and KN.

Almost all water conditioners are used according to the classical scheme – 5 ml of product per 50 liters of water.

In case of contact with the skin or mucous membranes, immediately rinse with clean water.

best water parameters for freshwater aquariums For different fishes

best water parameters for freshwater aquariums

Fish TypeTemperaturepHRigidity
Ancistrus+20 to +286.0-7.320-25
Guppy+19 to +297.0-8.512-15
marble gourami+23 to +266.1-6.8Up to 16
Danio+16 to +286.0-8.05-15
goldfish+17 to +296.9-7.28-25
lalius+23 to +286.0-8.0up to 20
macropod+16 to +266.5-8.06-20
Velifera mollies+23 to +287.0-8.5At least 10
Neon+22 to +266.8-7.0Up to 12
Cockerel+24 to +286.0-8.0Up to 15

Before placing fish of different species in the same tank, make sure that they need the same water and temperature, and are not harmless to each other.

Pregnant fish should be placed in a separate vessel or clean jar, partially filled with water in which the fish lived before, and, if necessary, added new settled water, checking all indicators.

Water changes in the home of the expectant mother should be carried out more often than usual. A suitable temperature is up to 28 ° C, since, at a higher level, childbirth begins in females.

best water parameters for freshwater aquariums 1

On a note! If the fish cannot give birth on its own, the temperature of the water rises on purpose.

saltwater aquarium treatment

Basic water preparation for a saltwater aquarium has the same rules as for freshwater.

The main difference is that so much sea salt should be added to the water so that its indicator is in the range of 1.021-1.024.

Such water is prepared exclusively in plastic containers.


Underwater inhabitants are no different from other pets and need special care. In order not to ruin the fish and plants, breeders should be responsible for the aquarium water treatment and further control its parameters.

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