4 Effective Ways How To Soften Aquarium Water

Have you been battling hard water in your aquarium? An aquarium water softener can help. There are several ways to soften aquarium water at home, and one option is to add a water softener cartridge or granular product to your tank.

This article will discuss what aquarium water hardness is, how to soften aquarium water at home, and the benefits of doing so.

What is Aquarium Water Hardness?

Aquarium water hardness is simply the level of calcium and magnesium present in the water. These minerals can form hard water scales, a problem for fish and other aquatic life.

There are a few ways to measure the hardness of aquarium water. One way is to use a pH meter, and the methods require that you have a good understanding of the pH scale.

Type of water hardness

There are two types of water hardness General hardness and carbonate hardness.

General hardness (GH) is the most common type of hardness, and the presence of minerals causes it. The presence of carbonates causes carbonate hardness (KH).

How to measure the aquarium water hardness?

Aquarium water hardness refers to the concentration of minerals in the water. Hardness can be measured in ppm (parts per million) or mg/L (milligrams per liter).

The higher the hardness, the more minerals the water contains. Mineral content in water can vary depending on where it comes from, but most municipal water supplies have high levels of calcium and magnesium.

These minerals can form hard water scales and cause fish and other aquatic life problems. You can use the pH scale.

What is the pH scale?


The pH scale measures the acidity or alkalinity of a solution. The pH scale ranges from 0 (most acid) to 14 (most alkaline).

Aquarium water can be measured in degrees of acidity or alkalinity using a pH meter.

The Ph scale is a way to measure the hardness of the water. It has a range of 0-14, water that falls within the range of 1-14 is considered “hard.”

Water that is too hard can cause damage to fish and other aquatic creatures. Water that is too soft can also cause harm, but it can also lead to bacterial growth and an increase in algae.

Ideal water hardness in an aquarium

The ideal water hardness for an aquarium is around 18 dH, and the 18dh level at which the water is neither too soft nor too hard.

Hard water can be challenging to keep clean and cause calcium build-up, while soft water can cause algae to multiply. Water hardness can vary from fish to fish. 

Ideal water pH in an aquarium

Aquarium water should have a ph of around 8.0-8.5 to soften water conditions effectively. Water pH is also varied from fish to fish.

How does aquarium become hard

Aquarium water becomes hard over time due to the accumulation of minerals and other substances, and tap water has high hardness because of the presence of minerals.

It is recommended to test the water before putting it in an aquarium.

Extra food lying bottom of the tank can also cause drastic changes in aquarium water parameters, and Low-quality water filters can cause this problem.

If you do not change the water regularly, this may also cause unstable water parameters.

Putting outdoor gravel or stone without proper cleaning may cause a sudden rise of hardness in the aquarium, mainly if limestone or any rock contains calcium. 

How to Soften Aquarium Water at Home

If your aquarium water is too hard, there are a few things you can do at home to soften it. One option is to add a teaspoon of baking soda to a quart of water and stir until the baking soda is dissolved.

Another option is to add a teaspoon of salt to a quart of water and stir until the salt is dissolved.

Peat moss filters

How To Soften Aquarium Water
Peat Moss

There are many ways to use Peat moss to lower the hardness of aquarium water.

Before trying to use Peat moss, do this.

Boil the peat moss for 2-3 minutes. This way, you can ensure that there are no contaminants left. Boiling can also prevent the excessive yellowing of the aquarium water.

Soften tap water using peat moss

If you live in an area with hard water, you can try to soften the water using peat moss. Fill a cup or container with peat moss and pour cold tap water into the cup or container.

Stir the water until the peat moss is fully submerged. Place the cup or container in a warm place for 24-48 hours. The softened water will now be usable for your aquarium.

Before putting peat moss into the water, you can boil it.

Use the Peat Moss in your filter media.

After boiling the peat moss, you can also put it in your filter, effectively boosting the water softening process.

Regularly test your aquarium water.

Peat moss releases tannin and gallic acid. Tannin can make your tank water yellowish don’t worry, this is natural.

But if you have boiled and cooled the peat moss. The yellowish effect will be reduced.


Rainwater is the cheapest way to soften aquarium water. If you use rainwater, you should perform all water changes.

Before using the rainwater, test the rainwater you have collected. Sometimes rainwater is high in GH and KH levels but naturally soft.

Rainwater sometimes can be too for your aquarium, so you have to make sure that the rainwater parameters match your aquarium water.

Use some tap water to harden your rainwater for your aquarium.

Safety measures for collecting rainwater:

The container should be “food grade.” They won’t leach any chemicals.

Make sure that the rainwater won’t get contaminated while harvesting.

If you live in an industrial area, do not use rainwater because that air is of poor quality and highly polluted. These areas are not ideal for collecting rainwater.

This is the best way how to soften aquarium water naturally but keep in mind where you live in.

Water softening pillows

Water Softening Pillows
Water Softening Pillows

Water softening pillows are among the best chemical filtration media for a small tank like 30 gallons. Water softening pillows are designed for lowering the general hardness of aquarium water.

The softening pillows contain ion exchange resins, which absorb calcium, magnesium, and other heavy metals ions.

You can reuse the water softening pillows. Soak the pillows in a brine (salt + water) for 2-4 hours to get them recharged.

The softening pillows are a great choice if you plan to bread soft water fish species like Discus.



You can also use Driftwood to soften the water in an aquarium, and Driftwood works the same as peat moss does.

Driftwood release acids that neutralize carbonate compounds. Using Driftwood has a downside and Driftwood can make your aquarium water tea color, and the color will remain for a short period.

Driftwood will soften water releasing tannic acid. Tannins are not harmful to fish. They can boost fish immune systems.

Driftwood can be harmful if you don’t keep this thing in check;

The Driftwood should be decontaminated before use. If your tank doesn’t have good aeration, fungi will grow on your Driftwood.

Reverse Osmosis (RO)

Why do you need to soften an aquarium?

Aquarium water can be hard and acidic, damaging fish and other aquatic life. Softening the water will make it more hospitable for fish and different marine life.

Soft Water Fish Species

  • Ram Cichlids.
  • Tetras.
  • Discus.
  • Barbs.
  • Cory Catfish.
  • Angelfish

The Benefits of Softened Aquarium Water

Softened aquarium water is a great way to keep your fish healthy and happy, and it can also help reduce the amount of maintenance you need to do on your aquarium.


Aquarium water hardness can be a challenge to deal with, but with the right tools, you can overcome it. We hope this article has helped you!

Softened aquarium water is beneficial for fish health and can help reduce the maintenance you need to do on your aquarium.

Hey, I am Shuvradeb Biswas a content writer. Fishkeeping is my hobby. There are many problems I faced during my first fishkeeping. So, I made the KeepingWorld.com blog to help new fishkeepers.

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