What kind of water is best for fish tank?

Water is a chemical compound consisting of two hydrogen atoms and one oxygen atom. It is a common solvent for many compounds.  In the case of fish, it provides a living environment for them. 

Aquarium water does not only consist of oxygen and hydrogen molecules but also contains a number of other compounds and elements.

The quality of your water is critical to the success of your fish tank. Your fish only live if the water quality is good enough for them to thrive.

Whatever water you decide to fill your tank with, you should test it first. It’s very important to have safe, clean, and reliable water when filling a new tank or performing a water change. Fish need water to survive, and the water that your fish lives in is very important.

What parameters should you take care of?

O2

The oxygen content in the water varies depending on many factors:

– the depth of the reservoir,

– water temperature,

– the presence of plants and animals.

In general, water in motion is more oxygenated than stagnant water. If the water remains motionless, only its upper layers are oxygenated. As the temperature rises, the oxygen saturation of the water decreases.

This relationship is inversely proportional. At lower temperatures, there is more oxygen in the water. This is because the fish tank water is oxygenated primarily from the air.

Oxygen in tank is also produced by plants. Oxygen consumers are fish and other aquarium animals, microorganisms living in the tank (in the gravel, filter), and plants at night. The availability of oxygen allows the breakdown of organic compounds into simple compounds that are easily digested by fish and plants.

Anaerobic processes in the tank lead to substances  that are harmful to fish. To increase the amount of oxygen in the tank, install a suitable filter, replace some of the water with fresh water or add more plants to the fish tank.

CO2

Carbon dioxide is excreted by fish and other aquatic animals. It is also excreted by plants during the night. Many factors contribute to high CO2 concentrations:

– overstocking,

– small amount of plants,

– wrong filtration,

– excessive fertilization of the substrate

Remember that an excessive amount of plants in relation to the fish leads to carbon dioxide deficiency during the day, and oxygen deficiency at night. Too many plants also affect the calcium content in the water.

Plants take up carbon dioxide from calcium bicarbonates and calcium carbonates. Excess carbon dioxide can effectively lower the pH. If you overdose the CO2 (more than 50 mg/l) the pH can drop to a level that is lethal for the fish.

The optimal amount of CO2 for good plant growth is 20-30 mg/l. However, the correct lighting should be kept in mind. In order for the plants to consume CO2 in the process of photosynthesis, the amount of light should be 0.5 W.

The table below shows how pH changes with the amount of carbon dioxide in the water.

CO2 concentration can be easily increased by using CO2 system.

pH

pH is a numerical scale that determines the reaction of water solutions. pH measures the level of hydrogen ions (H+) in water. A low PH means the water has more H+ than a high PH.

For the aquarist, the most important numbers are those that indicate whether the water is neutral, acidic, or basic.

In most cases, suitable water for fish is neutral (pH=7).

Water pH can be measured with a pH meter. This device is very accurate but relatively expensive. We can also use color indicators in the form of solutions (e.g.: methyl red, bromothymol blue), strip indicators available in pet stores, or pH paper (cellulose, litmus).

It is much more common to acidify the tank water than to alkalinize it. American, Asian and European fish prefer a pH in the range of 6-7.5. It is different for fish from the African lakes Tanganyika and Malawi. These prefer alkaline water. Too low a pH is dangerous for fish.

At pH=5 most plants stop growing and below 4.5 they die. We can lower the pH in several different ways:

– using distilled, demineralized or RO water

– by dosing CO2

– passing water through a filter filled with peat or alder cones (usually 8-15 cones per 100 l of water are used. Beware! It turns the water brown)

– dosing orthophosphoric or hydrochloric acid

– using special preparations available in pet stores

To raise the pH level we can use sodium carbonate or preparations available in pet stores. To keep the pH on a high level we should avoid activities that lower it and increase the KH.

Water parameters should not be changed when fish are in it. Also keep in mind that sudden changes in water parameters, including pH, may harm your fish. Parameter changes should be done in stages.

It is better to change too little than too much.

KH

Carbonate hardness (KH) is a measure of how many bicarbonate and carbonate ions are present in your water. KH is the ability of water to keep the pH level stable.

There is a correlation between the amount of carbonate ion bonds and the level of pH in the water. The more carbonates the more alkaline the water becomes, and the less the pH will drop. Having a healthy tank is vital. The KH determines the stability of the pH level in your tank. It impacts the health of your fish.

A Low KH indicates that your water is buffering poorly. It means that your water is not buffering fast enough to prevent a quick drop in pH. If your water has a low KH, pH can change quickly. It will be harder for you to change the pH of your water if KH is high because it has a high buffering capacity.

KH is measured in degrees of KH (dKH) or parts per million (ppm). 

1dKH = 17.9 ppm

There should be between 4 and 8 dKH (70 – 140 ppm) in freshwater fish tanks.

You can’t just add any kind of fish to a tank because it might not survive. Before introducing fish to a tank, make sure they meet the specific habitat requirements for that particular species. Many types of freshwater fish are intolerant of a constantly changing pH range. But if it is not too far out of the ideal range, fish can adapt to different pH levels.

It’s best to gradually change pH levels in your tank to ensure that your fish are comfortable. An easy and inexpensive way to raise the pH of a tank is to add baking soda. How to add baking soda correctly? First add the required amount to a bucket or pail, and then to the aquarium. It’s wise to remove the fish from the tank before changing the pH.

To keep your fish healthy, you should check the water in your tank every week. Small, consistent changes are better for your fish’s health than making sudden and dramatic changes. Aerate the tank with carbon dioxide or CO2 is a safe method of decreasing the pH. CO2 dissolves into water, creating carbonic acid, which decreases the pH.

How to increase KH?

– placing limestone stones, shells in the tank

– adding sodium bicarbonate solution to the water

How to lower KH?

– adding phosphoric acid or hydrochloric acid

– adding distilled or boiled water

GH

GH is a measurement of the amount of calcium and magnesium ions in the water. It is a general hardness measurement. The GH scale ranges from 0 – 30 dGH. If your GH is between 4 – 8 dGH, it is considered good for your tank.

To make sure your fish are happy, it is important to have a proper water quality and pH level. 

GH is measured in degrees of dGH (dGH) or parts per million (ppm).  There should be between 4 and 8 dGH (70 – 140 ppm) in freshwater fish tanks.

African cichlids, livebearers or goldfish require more GH than other fish. To breed discus, or other soft water fish, a lower level of GH in the water may be necessary.

If your tank has low GH, your fish may not be eating as well as it should. They may look lazy or begin to lose color. If you’re keeping shrimp in your tank, they may have trouble with molting. Snails can also have a problem. Their shell will be thin or pitted. 

If you have low GH levels, plants can suffer from electrolyte imbalances. By low GH the cause of the problem with plants can also be calcium and mineral deficiencies. 

Both calcium and magnesium are important minerals. It is crucial to remember that GH measures both. You may have high GH, but your plants and fish can thrive well. This may be due to the fact that the water in the tank has not enough calcium, but too much magnesium.

The GH level in your tank should always stay at the recommended level of GH to prevent your aquarium from getting sick.

The natural minerals you add to your tank water affect the pH, KH, and GH. You raise both GH and KH when you add calcium and carbonate ions.

KH helps to maintain the pH in a tank at its ideal level. To keep aquarium water in a healthy condition, it’s important to maintain a proper KH.

You should increase the carbonates and bicarbonates if the KH in the tank drops. It’s a good idea to get commercially prepared alkalinity buffers when you want raise the KH. 

How to increase GH?

– increasing the carbonate hardness KH

– adding non-carbonate magnesium and calcium salts

How to lower GH?

– lowering the carbonate hardness KH

– using distilled, demineralized water

Ammonia

Ammonia is an inorganic chemical compound of nitrogen and hydrogen. It dissolves very well in water.

This compound is formed as a result of the breakdown of proteins. The ammonia concentration varies with pH, ​​oxygen content and temperature.

High concentrations can kill the fish. 0.1 mg/l may cause fish poisoning, 0.2 mg/l is life-threatening, and concentrations above 0.5 mg/l are lethal for fish.  In a mature tank, the ammonia value should be 0 mg.

Ammonia can only be lowered by changing the water, reducing the pH and increasing the oxygenation. To keep your fish tank healthy, you need to maintain the correct nitrogen cycle, use proper filtration, and select the right number of fish.

Ammonium ions work in the same way as ammonia. However, they are much less harmful. Ammonium ions are compounds of ammonia linked to hydrogen atoms. They should not be present in a mature fish tank.

You’ll find that increasing the pH will reduce the amount of ammonium ions, but it will increase the concentration of ammonia. It’s pointless and it negatively affects the inhabitants of your fish tank. Prevention is the same as with ammonia.

Nitrites (NO2)

Nitrites are formed as a result of the oxidation and decomposition of ammonia and ammonium ion.

They are inorganic chemicals that are highly poisonous to our fish in high concentrations. In a mature tank, the nitrite content should be 0 mg / l. Concentrations above 0.2 mg / l are dangerous to fish, and above 1 mg / l can lead to death. Nitrite can be reduced by water changes or the use of adsorbents.

Nitrates (NO3)

Nitrite ions are oxidized to nitrates by Nitrobacter bacteria. Nitrates are found not only in the aquarium but also in other water sources. Low concentration is essential for plant growth.

Nitrates are absorbed by plants, but at higher concentrations it can cause algae growth.

We can reduce the level of nitrates by changing the water, adsorbents or by planting more plants.

By adding potassium nitrate, we can raise the nitrate level.

Phosphates

Phosphates are essential for plant development, but too high concentration can cause problems. Natural phosphates are produced by decomposing organic material, such as uneaten food, decaying plants and fish feces.

The level of phosphorus can be increased by adding special measures available in pet stores or by adding a solution of potassium dihydrogen phosphate.

You can lower the phosphate level by changing water, or by using water treatments like potassium nitrate or by using adsorbents.

Phosphates can be tested using tests from aquarium stores.

One thing that is very important in keeping your tank healthy is ensuring that your water does not contain high levels of phosphates.

Remember!

A high concentration of nitrogen or phosphorus doesn’t always mean that algae growth. The growth of algae depends on two factors: how much nitrogen is in the water and how much phosphorus is in the water.

Too high phosphorus content causes the development of cyanobacteria and a high nitrogen content causes the development of green algae.

The correct ratio of both N:P elements is 10:1 or 15:1.

Chlorine

Tap water is treated with chlorine, which is a very strong oxidant and disinfectant. In tap water, chlorine kills bacteria that can cause health problems.

Chlorine in tap water may vary from 0.5 to 2 ppm. Chlorine is also used to disinfect swimming pools.

Chlorine in water reacts with living tissues and organic matter, causing cell death in fish. The death of cells in fish gills leads to respiratory difficulty and asphyxiation.

When it comes to fish care, it’s best to treat your aquarium with care. Chlorine will poison fish when they are exposed to large amounts of it in their environment.

To keep the situation under control, the contaminated water must be neutralized quickly, or the fish must be removed from the tank.

Quickly removing fish (within three to six hours of exposure) from contaminated water can protect them from dying if they aren’t showing signs of respiratory distress.

There are a number of commercial water chlorination products that you can buy to quickly and safely remove chlorine from your tap water.

When it comes to testing water, you need to look for the following parameters:

• Ammonia
• Nitrate
• Nitrite
• Phosphate
• pH
• KH
• GH

What kind of water for fish tank?

Tap water

What kind of water for fish tank? The easiest and most obvious answer is to use tap water. The important thing is that all freshwater fish tank should use water that is clean and suitable for your fish.

We have as much tap water as we need – it’s cheap and easily available. Anyway, you are already paying for the tap water, so why not put that money to good use?

If you’re going to use tap water, it’s a good idea to know what contaminants you can expect in your tap water and how to avoid them. There are many types of water that vary in their quality. It’s not surprising that your tap water contains many different chemicals. The quality of your tap water is be determined by where you live.

Your local fish store should have a good source for using the right kind of water for your aquarium. You’ll get the best advice on how to use tap water to fill your aquarium from these experts.

Okay, so your tap water is safe to use? Then, there is just one more thing you need to do before adding it to your tank… Dechlorinate your tap water!

If your tap water is clean, you can add it to your tank right away. But remember to remove the chlorine from your tap water!!!

Most people don’t know the local water supply adds chlorine or chloramine to make it safe to drink. Chlorine is added to the water supply to kill bacteria, parasites and other micro-organisms that can cause illness and disease in humans and animals. Chlorine doesn’t care whether the bacteria are good or bad. It destroys everything.

Good bacteria are essential in your aquarium. You cycle your tank because you want to introduce good bacteria. As you learned earlier, chlorine kills all bacteria, whether they are good or bad.

Before adding tap water to your tank, you must first dechlorinate it. This treatment will not affect the beneficial bacteria in your fish tank. Adding a water conditioner is very easy I would recommend Seachem Prime. It’s a great product.

Prime dechlorinate your tap water, but it can also be used as a home treatment for ammonia, nitrite and nitrate poisoning. It will prevent many of the common problems that happen in a freshwater aquarium. It’s a good idea to have a bottle of this on hand.

Well water

Untreated groundwater that flows into your home is called well water. Depending on what your well water contains, it can be good or bad for your aquarium. Well water isn’t the same as tap water provided by your local water supply. Tap water is tested. It’s regulated. You need to get your own well water tested.

Different water types require different types of treatments. There are many factors that affect the hardness or softness of water, including the types of bedrock underlying a state’s water supply and the types of contaminants.

In states like New York and Colorado, groundwater is soft and easy to treat, while in states like Florida and Arizona the water is very hard and requires a more involved. The exact water parameters of your well water are completely dependent on where you live in the country.

The problem of unwanted pollution in a rural area can arise if there are many farms nearby.

Rainwater that enters into the groundwater can cause it to become contaminated. As a result, the water in your well can have a very high level of phosphates and nitrates. This water can lead to several problems in your aquarium

While you do need to treat your well water, at least it won’t have to be dechlorinated. Well water is chlorine-free. It’s a good idea to test well water frequently. 

Reverse osmosis water (RO water)

The reverse osmosis process creates a high pressure stream which flows through the membrane.

The membrane doesn’t absorb any substances, so it stops any dangerous contamination. Reverse osmosis is the most accurate method of water filtration. It removes more than 98% of contaminants from your water. In practice, a reverse osmosis system is usually installed in a cupboard under the sink. With reverse osmosis you will efficiently obtain water in the purest form. 

The water passes through the membrane and becomes purified.  Dirty water flows out in one line and purified water in the other.

The reverse osmosis process is a lossy process. Clean water is about 20-35% of polluted water. However, we must remember about a certain problem.

Reverse osmosis will not only filter out pollutants but also all the elements and minerals that are necessary for our aquarium. We need to provide all the necessary minerals to the RO water. In the case of fresh water, we can use a remineralizer. I recommend Seachem Equilibrium.

Depending on the system, a reverse osmosis system can cost anywhere from $50 to $300. The filters need to be replaced at regular intervals. If you have soft water, you can get up to 2 years of use before you need to replace the filter. Hard water may need to be replaced every 6 months.

Deionized water (DI water)

You can also purchase a deionization unit that attaches to your home’s plumbing system. Reverse osmosis doesn’t work the same way as deionization, but it is a form of water filtration. 

Deionization (DI) is a very efficient and effective method for removing most contaminants from water. It’s a very convenient and cost-effective method for producing highly purified water on demand for  aquarium use.

Ion-exchange resin, commonly abbreviated as ion exchange resin, is a solid organic polymer compound or an inorganic compound that has exchangeable ions. Water deionization removes many types of contaminants, such as minerals and even man-made chemicals. 

One drawback with DI systems is that they do not remove bacteria or sediments from your water. The deionization system can remove more contaminants than RO system, when used correctly. Before using Di water in your aquarium, you need to remineralize it.

You will not usually buy a de-ionizer (DI unit) on its own. They are used in addition to an RO system, which means they are a great way to increase the efficiency. 

You need to find a way to purify your water. When water is not balanced properly, it may make dramatic changes in pH, alkalinity, and hardness when exposed to chemicals. You should use RO or DI water to keep the water clean and free of harmful chemicals.

People start using RO or DI water before they have the knowledge and experience of how to do so safely. If you don’t know how to do it right, give yourself some time.

RO/DI water

There’s more than one way to filter water. If you’re looking for a water filtration system that combines the benefits of reverse osmosis and deionization, take advantage of both filtration methods. A RO/DI water filtration is a great choice.

A combination of these techniques creates water with a purity far beyond what could be achieved by any of them individually. Here’s the result: the purest water imaginable, right in your own home.

Distilled water

If you rarely need to purify your water, using distilled water will be the best solution for you.

Distillation is the process of boiling water, until all of the volatile components have evaporated away. The water then cools, leaving behind a residue (or distillate) of purified water. The process of boiling to remove volatile compounds from a liquid is called distillation.

If you want the most pure and healthy water, then buy a bottle of distilled water. You can find gallon of distilled water for $1 in your local grocery store.

Most people, no matter whether they’re living in the countryside or in a city, have water with varying amounts of minerals, bacteria, pesticides, and other contaminants. Distilling helps to remove the impurities from the water. Not only does it remove all those nasty impurities, but it also removes 99.9% of the minerals dissolved in water.            

Distilled water isn’t practical for larger tanks. Although distilled water is inexpensive, we need around $100 to fill 100 gallon tank.   

And it’s important to add enough minerals to the water to make sure that it is balanced and that the proper amount is in your aquarium.

Bottled water

I wouldn’t recommend bottled water unless your local tap water is unsafe or you do not have access to other water. 

Bottled water is often not regulated or tested, so we don’t know exactly what the water contains. Bottled water is full of artificial substances that are added to make the water more appealing.  Bottle water is good for you, but it’s not the best solution for a healthy aquarium.

There are three different types of bottled drinking water: purified water, spring water, and filtered water.  All of these water have different parameters. You need to test your bottled water carefully before adjusting it.

Bottled water is designed for humans to drink, so it’s generally much more expensive than simply using distilled water. You can choose bottled water if you’re in a hurry or if you cannot use other water.

Rainwater

There are people who are interested in using rain water for their fish tank.

All you need is a rain barrel or storage tank and you’re ready to start harvest water. However, you won’t do it if it doesn’t rain. If you live in a desert state like Nevada, this can be a big problem. If it’s raining frequently, then you have no need to worry. But if there is no rain you risk running out.  In such a situation, we must have another source of water.

Rainwater is often lacking in many important nutrients that are needed to keep the fish healthy, and also lack of those needed to keep the water balance. Rainwater is acidic, so it should first be neutralized. Then it can be safely used in your fish tank.

Rainwater that has flowed through the soil or is sitting on the surface of the ground or roof has a high chance of having been contaminated with pollutants from these sources. It should be tested for water quality before you use it for any purpose. Also collecting rainwater from the roof isn’t going to provide a healthy environment for an aquarium. Even more so if there is asbestos on the roof.

Rainwater can be contaminated by air pollution. Cities in the United States are notorious for their heavy pollution.

The water barrel is the perfect place for mosquitoes to lay eggs. Mosquito larvae are great for your fish to eat. However, it is up to you to ensure that your neighbor is satisfied with the mosquito infestation. 

Rainwater can be an alternative to aquarium tap water as long as you overcome the above obstacles.

Natural waterways

Many people assume that water from lakes and rivers would make great water sources for their fish. 

It’s hard to resist the temptation to collect water from a nearby stream, river or lake for your water change. In fact, I do not recommend using such water source.  

These fish were only here for generations. They have adapted to the conditions. They are totally adapted to living in that water. On the other hand many waterways in the US are polluted with toxins and other pollutants that make them unsafe for fish to live in.

It looks as if the water is clean, but it may contain toxic chemicals. Don’t depend on a basic aquarium test kit to make sure it’s safe. While tests that can identify this pollution are available, they are too expensive to make the procedure practical. 

When it comes to waterways, they’re full of fish, insects, micro-organisms, fungi and parasites. No freshwater fish are prepared to face these nasties. 

So stay away from your local river. Water from  rivers, streams or lakes can be dangerous to your fish !!! The long and the short of it: Using water from rivers, streams and lakes can be dangerous to your fish.

Water from another tank

If you have access to water from another aquarium, that is another possibility.

Water from another aquarium can be helpful for setting up a new tank. It can be helpful but you can’t cycle your new fish tank with the water from an already cycled fish tank. You should remember that beneficial bacteria that you are trying to foster live on the surface and not in the water column itself. 

f you don’t know the history of the tank, it could be a risk of disease or chemical toxicity to your fish. The history of the tank and water conditions can make or break the quality of the aquarium and its health. Get to know these details before you take water from another aquarium. 

And something else. You should not use water from another aquarium for periodic changes!!!

In conclusion

The water you use for your fish will affect whether your fish live or die.

Selecting the right water source can make it easier to maintain water quality. Remember that testing is the most important thing. 

What kind of water do you use to fill your fish tank? I’d love to hear from you in the comments below.