How To Soften Water In A Home Aquarium Or Fishbowl? (5 Easy Peasy Methods)

Water quality is vital when rearing fish in a body of water like an aquarium. The quality of water has a direct impact on the life and survival of the fish. If the water is hard or very hard, the chances of your fish surviving are slim, especially if your fish specie isn’t trained to survive in such an environment. If the fish isn’t compatible with the type of water, you might have a little problem.

It is widely accepted that over 97% of all living animal species require clean and healthy water to survive. However, the water quality in aquariums is not always up to par with this standard. Aquaria contain hard water, which can harm fish and other aquatic life by reducing their immune systems.

You need to take action immediately to save your fish. By reducing calcium and magnesium concentrations in aquarium water, you can soften it. The process of water softening can include deionization, chemical filtration, or peat moss/driftwood. Read on to learn more about this.

Table of Contents

How Do You Determine Whether Your Aquarium Water Is Hard or Soft?

If you are unsure about the quality of your aquarium water, there are ways to test for that. This is how to determine whether your aquarium water is hard or soft.

Soapsuds test

This step is more like for DIY people. We find this method the simplest among them all. The reason for saying so is that it won’t take more than ten minutes to figure out whether your water has gone hard. You stay in your comfort zone and carry out the testing yourself.

Test kits

Insert the test strip into a container filled with aquarium water, and wait for a few minutes. Test strips come with color charts, so observe the color change. The corresponding color change in the water with that of the color chart will determine if you have a soft water aquarium or not.

Measure the PH value of your water

Most people have access to a digital meter that allows them to check the PH of their water. Alternatively, you could also buy a cheap glass bottle with a built-in PH gauge.

Determine the Specific Gravity of your water

Using a refractometer, you can calculate the SG of your water. Refractometers are inexpensive and easy to operate. They compare the refraction index between two liquids, usually air and water. By calculating the difference in the indices of refraction, you can determine the density of the liquid being measured.

Test with soap suds

If the soap turns colors in your aquarium, it is hard water. If the soap does not turn colors in your aquarium, it is soft water.

How to Soften Aquarium Water Naturally and Chemically

To most aquarists, reducing the number of mineral contents in the aquarium is of utmost concern. Once in a while, the water in your aquarium may turn hard; when it does, you need to find a way to soften it.

Luckily, you don’t need to go to a great length or find some sophisticated tools and chemicals to soften aquarium water. At first, it may seem tedious, especially if you don’t know how to go about it. Below is how to soften aquarium water naturally.

Reverse Osmosis

Reverse osmosis is a method of purifying water by forcing it through a semi-permeable membrane. Pure water passes through the membrane as long as the pressure applied remains constant. Reverse Osmosis units come in both manual and automatic versions.

While they are good for treating large volumes of water, they cannot handle small liquids. It would be better to pour boiling water directly onto the tank if you soften only a few gallons.

Water Softening Pillows

A water-softening pillow is like a mesh or net that helps to soften the water’s hardness in aquarium water. These softening pillows contain sodium ions, which, when used, replace calcium and magnesium in the water. For best results, place the pillows in the filter of the aquarium.

One great benefit of using this method is the mesh can be reused. You must dip it into a salt solution and place it back in the filter.


You can use rainwater if you want to escape the stress of using various water-softening techniques. Rainwater has so many benefits that one can’t simply imagine.

Rainwater is the purest form of water, making it ecologically sound for use as aquarium water. You can drain some of the existing water in the aquarium and replace it with rainwater. All you have to do is make sure you catch enough in your large containers or clean buckets.

You must be careful about using rainwater in a pollution-stricken environment. Using polluted water will harm the fish in the aquarium. The rainwater to be used is to be clean, devoid of any chemical or industrial pollutants.


Peat is a type of soil composed primarily of partially decomposed plant material. It can be used in aquariums to help soften the water and reduce the number of ammonia and nitrite spikes. However, peat is not recommended for tanks with fish that need more specific and stable water chemistry.

Peat tends to break down quickly, releasing nitrogen into the environment. So, it is advisable to avoid using peat unless necessary.


Using fresh, clean driftwood is another alternative to softening water in your aquarium. It may not be as effective as others mentioned earlier, but there’s certainly no harm in keeping your options open.

Driftwood will make your aquarium brownish unless you soak it in a container before using it in the aquarium. Boil the driftwood before use to remove any toxin that’s present. Remember, you are free to leave the brownish color if you want. It wouldn’t harm the fish inside.

Reason to Use Reverse Osmosis Water for Your Aquarium

Reverse osmosis is ideal for aquariums because it produces water of the highest purity. It removes up to 99% of dissolved solids, chemicals like chlorine, and toxins from the water, creating a neutral environment perfect for fish to thrive. This allows you to design the precise water conditions that best suit your aquarium without being restricted by your local water quality.

Reverse osmosis also eliminates heavy metals, nitrates, salts, and dissolved minerals from the water, leaving behind incomparable purity and an inimitable blank slate from which you can craft your aquarium environment.

The pH levels of the water you use, the salt content, and the minerals that are exposed to your aquatic life can all be controlled by reverse osmosis. In this way, you can provide a healthy and comfortable environment for your fish.

Why Should You Soften Your Aquarium Water?

In essence, the reason for softening water is to lower the amount of calcium and magnesium content inside, thereby promoting osmoregulation. Osmoregulation is the balance of salt and water inside fish’s bodies with those outside. Osmoregulation, in a nutshell, is a process fish use to survive in water.

To keep your fish from dying, you should soften the water in your aquarium. There are a few reasons for this:

Hardness Levels Affect Fish Health

As discussed earlier, hard water causes several harmful effects on fish. These include decreased immunity, poor digestion, and increased stress. Hard water also increases the risk of disease outbreaks among fish. Because of this, you must regularly monitor the hardness of your water and take action whenever necessary.

Reduce Chlorine Use

To prevent bacteria from growing in pipes, chlorine is often added to municipal drinking water. This is good, but too much chlorine can kill beneficial organisms like nitrifying bacteria. Most municipalities recommend 1 ppm free chlorine when using tap water to prevent microbial growth.

The problem is that even though this concentration is safe for humans, it is extremely toxic to fish. To avoid killing off valuable microorganisms, try reducing the amount of chlorine in your tap water.

Increase Plant Growth Rate

Plants need certain minerals to flourish. One mineral that helps plants grow faster is calcium carbonate. Unfortunately, CaCO3 dissolves very slowly in hard water. As a result, plants do not get enough nutrients to develop properly. If you want to speed up plant development, you must add extra calcium carbonates into your tank.

Improve Cleaning Efficiency

If you live in areas where rainfall is heavy, then you know that hard water forms naturally. Even if you don’t experience any rainstorms, the hard water still builds up in your home due to evaporation.

Hard water contains more salt than regular tap water, so filtration takes longer to remove impurities. By softening your water, you’ll be able to improve the efficiency of your filter system.

Prevent Scale Buildup

Calcium ions form insoluble compounds called calcite or aragonite when they bind together. Calcium ion accumulation leads to an imbalance between positive and negative charges in the body.

A negative charge deposits itself on surfaces like rocks, gravel, and plastic parts of your aquarium. Over time, this buildup can clog your plumbing and damage your equipment.

What’s the Perfect ph for an Aquarium or Fishbowl?

The pH of water measures its acidity (pH 1 to 7.0) or basicity (pH 7.1 to 14). It is considered neutral when it reaches 7.0. Generally speaking, tropical fish in freshwater aquariums thrive at a pH of 6.8 to 7.8, although some fish require a higher or lower pH. If you want your fish to be healthy, safe and sound, then maintain that ph.

Frequently Asked Questions [FAQs]

1. Why is My Aquarium Water Cloudy?

If your aquarium is cloudy, it could be a sign that the water is hard. All you need to do is remove the minerals that cause the hardness. We have mentioned the methods you can use to soften your aquarium water.

2. Aquarium Water Change Frequency?

You should change up to 25% of the aquarium water every two weeks to one month. You shouldn’t change more than 30% of the water in your aquarium because you will remove beneficial bacteria from the tank.

3. What Are the Aquarium Water Testing Kits?

These are testing kits that you can use to determine the hardness of the water. The testing kits come with color charts and come in different forms.

4. Will Hard Water Kill Fish?

Hard water won’t kill the fish if the fish is compatible with the water environment.

5. Should Aquarium Water Be Hard or Soft?

That depends on the source of the water. Some fishes survive in hard water, while others survive in soft water. You should know if the water in your aquarium is soft or hard. This will go a long way in determining the type of fish to rear.


Now that you know all that needs to be known about softening aquarium water, what’s next? The next thing is to start to implement the methods that are most convenient for you. Scan through all the information in this article and ensure that you tend to your fish the best way you can.


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