how to soften aquarium water

How to Soften Aquarium Water With 6 Proven Methods

We are all looking for ways to make our aquariums more enjoyable for our fish. One of the key elements in achieving this is making sure that the water is properly softened.

Hard water can be a major issue in an aquarium, but the question is how to soften aquarium water?

Luckily there are some simple solutions that will help you soften it up. In this article, we’ll look at what hard water is and how it can impact your fish, as well as how to test for it and how to soften it up.

Hard Water: A Concern

We know that hard water can be a major problem for an aquarium. It can stunt the growth of fish & plants and affect pH levels. It can even lead to the death of some species of fish.

Hard water is caused by high levels of minerals in the water, such as calcium and magnesium carbonates. Tap water can contain up to about 300 parts per million (ppm) of these minerals, which is considered too hard for most aquariums.

To soften this type of water, you’ll need a good quality water softener or de-ionizer. These products help remove excess minerals from tap water so that it’s safe for your aquarium inhabitants. 

How Is Water Hardness Measured?

You can measure the hardness of your water by testing its General Hardness (GH) and Carbonate Hardness (KH). This will give you a sense of how hard or soft it is.

Water HardnessGeneral Hardness (GH)Alkalinity (KH)
Very soft0-4 dGH0-4 dKH
Soft4-8 dGH5-7 dKH
Slightly hard8-12 dGH7-8 dKH
Moderately Hard12-18 dGH9-12 dKH
Hard18-30 dGH13-20 dKH
Very hard>30 dGH>20 dKH
Source: fishkeepingwisdom

Fish tank water softener products are available to help lower the hardness of aquarium water if needed. These products work by exchanging cations in the water with sodium ions, thus reducing the amount of calcium and magnesium in the water, which makes it softer.

Additionally, adding live aquatic plants to your fish tank has also been known to reduce hardness in aquariums. This is because the plants absorb some of these minerals from the water. Therefore, there are several ways that you can soften aquarium water in order to create a healthier environment for your fish.

How To Test Water Hardness In Aquarium Water

To accurately measure both General Hardness (GH) and Alkalinity or Carbonate Hardness (KH) for your aquarium, you’ll need 2 different tests – a GH Test Kit and a KH Test Kit.

Test General Hardness (GH) Of Aquarium Water

To accurately assess the hardness of your aquarium water, you can use a general water hardness test kit. This test measures the concentration of dissolved calcium and magnesium in the water and provides readings on a scale from 0-12 dGH.

Lower values indicate softer water, while higher readings indicate harder water.

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Test Alkalinity or Carbonate Hardness (KH) Of Aquarium Water

Testing Carbonate Hardness (KH) is an important step in maintaining stability in your fish tank’s water quality. It is measured by placing a few drops of carbonate hardness test solution into a sample of aquarium water and then comparing the results to the color chart that comes with the test kit.

Tannic and gallic acids can be added to lower the KH level, while acid buffer solutions can be used to raise it if needed. Therefore, testing KH regularly is essential for keeping a healthy environment for your fish and other aquatic creatures.

Surprising creature: The Amano shrimp, which can be used as an indicator species for KH, will also demonstrate changes in carbonate hardness levels when placed in the tank.

Amano Shrimp

How To Soften Aquarium Water?

We’re here to discuss the ways on how to soften aquarium water.

  • Indian Almond Leaves release tannins into the water, which reduces pH levels and makes water to acidic water.
  • Driftwood also releases tannins that can help in softening aquarium water.
  • Rainwater harvesting helps in providing soft water with low mineral content compared to tap water.
  • Reverse Osmosis is a process involving a filtration system that removes most of the dissolved salts present in hard water, making it softer and purer than before.
  • Peat Moss improves the acidity of the tank’s environment, which eventually leads to a decrease in the hardness of aquarium water.

Let’s check more details: –

Indian Almond Leaves

You can easily soften aquarium water with Indian Almond Leaves, bringing balance and harmony to your aquatic environment.

Indian Almond Leaves

By adding Indian Almond Leaves to the tank, you’ll create an acidic environment that is essential for some Asian species. It also helps to reduce the alkalinity of the water.

The leaves also provide tannins and other beneficial substances that are great for fish health.


We love using driftwood in our aquariums. Not only does it add a touch of natural beauty, but it also softens the water by releasing tannic acid.

While this can give the water a brownish tinge, the tannins are harmless to fish and can even boost their immune systems.


It is necessary to monitor for fungal growth in tanks with driftwood, especially those that aren’t well-aerated.

By incorporating driftwood into your aquarium, you’ll be able to enjoy its many benefits without worrying about any negative side effects.

Rainwater Harvesting

Harvesting rainwater can be a great way to add natural elements to your tank.

To ensure you’re getting the best quality water for your aquarium, it’s important to choose a rainwater harvesting method that keeps the water clean and free from contaminants.

Women capturing Rainwater

Using food grade containers is ideal as they won’t leach any chemicals into the water.

Additionally, it’s best to avoid collecting rainwater from industrial areas with poor air quality or high pollution levels.

Reverse Osmosis

Reverse osmosis is a reliable way to demineralize and deionize water, removing up to 99% of impurities while blocking large molecules like minerals.

It’s a great solution for softening aquarium water; it’s more efficient than other methods like additive peat or chemical methods. The carbon filter removes any remaining particle impurities.

RO makes an excellent investment if you’re looking for a long-term solution; it can save time and money in the long run when compared to other softening methods.

Peat Moss

Having discussed Reverse Osmosis (RO) as an effective method for softening aquarium water, let’s now look at another option: Peat Moss.

Peat Moss

Peat moss, when used as a filter media, binds calcium and magnesium ions in the water to reduce hardness – a process known as chelation. This demineralization also leads to the release of tannins and gallic acid, which lowers KH and pH levels by neutralizing carbonate and bicarbonate ions.

Here is an bullet list of 4 items outlining some key points about using peat moss:

  • Boil the peat moss before using it – this’ll decontaminate it.
  • Dispose of the brown water and place the cooled peat moss in a clean container filled with tap water.
  • Keep peat moss in the container for a minimum of 2-3 days, allowing the water to soften.
  • When conducting a regular water change in your aquarium, use the softened water.
  • Test the levels of General Hardness (GH), Carbonate Hardness (KH), and pH inside the tank to ensure water quality remains stable.
  • Repeat the process as needed to maintain the desired water conditions for your fish.

Water Softening Pillows

Water softening pillows are an effective chemical filtration media specifically designed to soften aquarium water by removing calcium, magnesium, and other soluble heavy metal ions through an ion exchange process releasing sodium ions.

Their use is limited to smaller tanks (<30 gallons) as they need to be recharged every 48 hours with a brine (salt + water solution). This makes them a great option for those looking to lower GH in their tank without having to waste too much time or energy.

Why We Need To Soften Aquarium Water?

There are several reasons why it may be necessary to soften aquarium water:

1. pH balance: Some fish species like freshwater angelfish, neon tetra require specific pH levels in order to thrive. Softening the water can help achieve and maintain the desired pH range for these fish.

2. Hardness: Some fish are sensitive to high levels of hardness and may be prone to health issues if kept in hard water. Softening the water can reduce the hardness and create a more suitable environment for these fish.

3. Breeding conditions: Certain fish species like discus fish require soft water for successful reproduction. Softening the water can help replicate their natural habitat and improve breeding conditions.

4. Sensitivity: Some fish are simply more sensitive to water conditions and may not be able to tolerate hard water. Softening the water can provide a more comfortable and stress-free environment for these delicate fish.

5. Plant growth: Soft water is often preferred for aquarium plants, as it allows them to absorb nutrients more easily. Softening the water can promote healthy plant growth and create a more aesthetically pleasing aquarium.

It’s important to note that not all fish require soft water and some may even prefer harder water conditions. Before deciding to soften the water, it’s crucial to research the specific needs of the fish species you plan to keep in order to provide them with the best possible environment.

Which Are The Fish Species That Can Survive As Per Water Type?

We’re discussing which fish species can survive as per water type, with a focus on hard and soft water fish.

Hard water generally contains minerals such as calcium and magnesium that make it difficult for some species to thrive. Soft water has fewer of these minerals, so certain species are better suited for this environment.

We will explore which fishes are best suited for each type of aquarium water in more detail.

Hard Water Fish Species

Don’t want to take care about Hard water!

Check out these hard water fish species that love living in a tank with higher levels of general hardness.

Hard Water FishGeneral Hardness (dGH) Range
Paradise Fish5-30 dGH
Mono Fish8-14 dGH
Guppy Fish8-12 dGH
Swordtail Fish12-35 dGH
Platy Fish10-28 dGH
Molly Fish15-30 dGH
Archerfish20-30 dGH

Soft Water Fish Species

Soft water fish species are perfect for those looking to add a touch of diversity to their tank, as they thrive in low-mineral streams with general hardness levels below 8 dGH.

Soft Water Fish SpeciesGeneral Hardness (dGH) Range
Tetras2-10 dGH
Cichlids3-6 dGH
Angelfish3-8 dGH
Discus3-8 dGH
Barbs3-10 dGH
Cory Catfish3-10 dGH
Gouramis5-10 dGH
Apistogramma Dwarf Cichlids3-12 dGH
Rasboras4-12 dGH

Also read: Uncovering The 5 Best Place To Buy Aquarium Fish Online in India


We’ve learned that hard water can be a major concern in aquariums. It’s important to measure, test, and soften aquarium water so that it provides the best environment for your fish. By understanding how to soften aquarium water, we can create an optimal habitat for our aquatic friends.

Doing this will also help maintain the health of our fishes, ensuring they live long and happy lives! With proper testing and softening techniques, we can make sure our fish are living in a safe and healthy environment.

Frequently Asked Questions

  1. How often should I test the hardness of my aquarium water?

    We recommend testing the hardness of your aquarium water every week to ensure it stays within a safe range. Regularly monitoring will help maintain the desired balance for your fish, allowing them to thrive in an environment that offers freedom and security.

  2. Are there any plants that thrive in harder water?

    We’ve found some aquatic plants that thrive in harder water. Swordplants, Vallisneria, Anubias, and Java Ferns are all great choices. They can help maintain a healthy aquarium while adding color and life to the environment.

  3. Do I need to do anything to maintain the softness of my aquarium water?

    We need to regularly check the water’s pH level and hardness, as well as keep up with regular water changes. Doing this will help maintain the softness of our aquarium’s water.

  4. What type of filter do I need to soften aquarium water?

    We need a filter that removes harmful minerals and chemicals from the water. A reverse osmosis system, activated carbon filter, or deionization unit can all help soften aquarium water and keep it that way.

  5. Are there any natural ways to soften aquarium water?

    Yes, there are natural ways to soften aquarium water. Using peat moss or driftwood, adding a bubbler, and regularly performing partial water changes are all great methods for softening water.



Meet me, your dedicated author and fish aficionado. With a deep-rooted passion for all things aquatic, I bring a wealth of knowledge, experience, and enthusiasm to this fish and aquarium website. As an avid fishkeeper myself, I understand the joys and challenges that come with creating a thriving underwater world. Through my articles, guides, and recommendations, I strive to provide you with accurate, reliable, and engaging content that will enhance your fishkeeping journey. Join me as we dive into the fascinating realm of fish and aquariums, and together, let's make your aquatic dreams a reality.

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