How to soften aquarium water?

There are a number of things that you could try to soften aquarium water. You could buy a water softener that will use iodized salt to soften the water. You could also buy a reverse osmosis system which will filter out all the minerals from the water.

Both of these systems require water to be run through the system and therefore would not work in an aquarium.

here are some methods that you can use in your aquarium to soften or lower the hardness of the water.

  • Driftwood
  • Iodized salt
  • Rain Water
  • Water softener
  • Reverse Osmosis
  • Commercial rinses
  • Tap water conditioner
  • Vinegar and baking soda

Soften Aquarium water using Driftwood

Hemlock is a form of driftwood that can be used to lower the hardness and pH in an aquarium. This is because it contains tannins which are great chemical substitutes for the hard minerals found in other types of driftwood. These tannins are very helpful in breaking down bacteria, removing ammonia from the water, and lowering the pH.

Soften Aquarium water using iodized salt

The process of softening water requires a great deal of salt. The types of salt used are usually iodized salt or normal table salt. When the water is softened, its ionic charge is reduced and it becomes more soluble in water. This is what makes it easier to wash away the minerals in hard water. Some types of salt are better at this than others and iodized salt is best for aquariums because it provides a number of important trace elements.

You need to be very careful when using this substitute to soften your water. You cannot use regular table salt or sea salt because these are not the same as iodized salt. Table and sea salts contain heavy metals which can be toxic to your fish, invertebrates, and other aquatic life. Professional aquarium water softeners also use these types of salts because they should not affect any other elements in the water besides hardness.

Soften Aquarium water using Rainwater

Rainwater is another substitute for softening your aquarium water. This process is known as osmosis and it works by using the ionic charge of water to move through a membrane. The membrane will stop any minerals from passing through but the rainwater will be able to pass through because its ionic charge is lower than that of the hard minerals.

The idea is not 100% effective because some minerals may still get through and there are also other chemicals and impurities in rainwater that can affect your fish’s health. It is best to only use this solution if you live in an area where there is plenty of rainfall like the tropics or near a mountain range with thick soil cover.

Soften Aquarium water using water softener

A water softener is a great option for people with hard water. It will use some type of salt to soften the water. There are a couple of different types of salt that can be used but iodized salt is best for aquariums because it will provide a number of important trace elements.

Soften Aquarium water using Reverse Osmosis

A reverse osmosis filter is a type of water purification system that filters out all minerals from the water.

The solution to your problem is to buy a reverse osmosis system and a salt softener. This system will make water soft using the salt and then filter out all minerals using the reverse osmosis system.

Soften Aquarium water using commercial rinses

There are a number of commercial rinses that fish keeping hobbyists can use to lower the hardness or pH temporarily but they are actually designed to remove chlorine from the water used for aquariums after it has been treated with a chlorinator. These cannot be used to alter the general hardness or pH of the aquarium water.

Soften Aquarium water using tap water conditioner

Tap water conditioners are also used to soften water. This is actually a saltwater mix that you put back into the tank after you have taken out all of the impurities.

You can do this with every change of the water or just keep an eye on your calcium and magnesium levels and add it when they get too high.

Soften Aquarium water using vinegar and baking soda

The easiest way to soften your aquarium water is by adding a combination of vinegar and baking soda.

Start off with about 10 ml for every liter of water and then check it after a few hours to see if it has reached the correct level of softness.

If you find that there is still some hardness left then add a little more vinegar or baking soda to achieve the desired level. This method can be a bit slow for those who want instant results but it will work effectively and safely in getting that soft water intake.

Benefits of softening Aquarium water

The biggest benefit of having soft water in your aquarium is that it will not cause any harm to the fish and aquatic life.

The pH balance will also be better because more nutrients can be absorbed into the substrate.

Soft water also makes it easier to clean the tank which is something that most hobbyists find very difficult to do when they have hard water.

It also helps remove scaling so that you don’t have to clean the glass of the tanks so often.

Another benefit is that the fish will be able to swim more freely because there won’t be any slippery mineral deposits or hard scale buildup on the tanks.

Soft water will help protect your plants and aquatic life from stress. This is especially important if you are introducing new fish to the tank.


So, while not an instantly obvious way to make water for your aquarium soft, adding some vinegar and baking soda can really help. There are also a few other solutions that I recommend trying before you go for the low-cost water softener with salt mix.

For more information about soft water and aquarium fish feel free to ask!