Can You Use Softened Water In A Fish Tank?

Most fish tanks do not contain softened water. Soft water aquaria often have fewer dissolved minerals, the results in the alkalinity reserve being very low. Water softeners used indoors often work by substituting calcium and other minerals in the water with sodium.

So can you use softened water in a fish tank? The answer is yes but there is a catch. Water softened by household domestic water softeners cannot be used in a fish tank. There’s not a lot left in softened water to mop up acidic chemicals. This then leads to an accumulation of sodium and lowers the pH level affecting the water chemistry. Later on, in this write up, I am going to explain further.

Is Tap Water Safe for Aquarium?

The water we drink, use in washing, cooking and even filling our fish tanks is loaded up with dissolved minerals. You may not need to worry about this as the regular tap water contains all these minerals. Even I didn’t realise this early. But over the years, I have had the opportunity to study water from a chemical point of view and I discovered that there are two types of water – hard water and soft water.

I also found out two other things. Firstly, that tap water is ‘hard water’ and is the right type of water for most breeds of fish. It is loaded with lots of calcium and magnesium which is important for the growth and development of fishes and that the story, unfortunately, is very different from soft water. This type of water has less dissolved minerals and can be introduced into your fish tank in small amounts.

Over time, the mineral contents within tap water can lead to a headache if consistently used. It will eventually lead to a dangerous build-up of chemicals leading to fish death. It is important to have a filtration system feeding into your aquarium water to help ensure your fish have a happy healthy existence.

How is Water Hardness Measured

“Parts per million” (ppm) of calcium carbonate, and “general hardness” of calcium (GH) are the standards of measuring how hard or soft a water sample is. Soft water was discovered to have less than 135 ppm and 4 to 8 gH, while hard water was found to have at least about 200 ppm and 12 to 20 gH.

I know you may be inquisitive now and want to find the ppm and gH values of your tank. To find this out, it is simply a case of using a water hardness kit, you can measure the GH levels of your fish tank. With some additional tests, you can also measure the PPM in your water aquarium.Can You Use Softened Water In A Fish Tank?, Aquarium Fish Tanks UK

If you find this too difficult a task, you can simply call your water utility company to make enquiries. While keeping fish is not their job, it is their job to keep track of water hardness.

Testing for Water Hardness

Another key indicator is to check the amount of calcium carbonate in the water. It is also a way of telling if your water is hard or soft. The carbonate hardness kit is used to run this test. It can be done using a simple titration technique.

All you need to do is simply add a few drops of the chemical to the water sample, and the number of drops required to change the colour of the water-plus-chemical mixture tells you the calcium carbonate (kH) level. Some kits come with already treated paper strips which can also test the KH level of the water. To do so, just dip the strip into the water and it tells you the range. ‘Simple’.

The degree of softness of water is defined by the amount of calcium carbonate it poses. Moderately soft water has about 50mg/l to 100mg/l of calcium carbonate while very soft water has less than 50mg/dl of calcium carbonate.

Using soft water for a fish tank is not supposed to be a big problem. The problem arises when the water is too soft. Very soft water has very little calcium carbonate, and this calcium carbonate is supposed to be a natural buffer. So in its absence, the pH of your water is allowed to easily fluctuate, this means it could easily change from a pH of 7 which is neutral to a pH of 5.6 which is acidic and can kill your fishes in a very short time.

If you notice that your water is too soft, all you have to do, to easily solve this problem is filter it through crushed coral or dolomite.

The minerals form these compounds will leach into the water and make it hard, even though it is a little, therefor increasing its calcium carbonate value and consequently its resistance to pH changes. The only problem you will face after this is that the coral and dolomite don’t add calcium and magnesium to the water, which is essential for the survival of your fishes and plants.

Soft water is readily available in areas where water flows in a low mineral containing regions. It is what makes up most of the water bodies around South America, Southeast Asia and West Africa. Because many of the fishes we keep in our aquariums come from these regions, people are made to believe that soft water is the right and better type of water for our fishes. Yes, this may be true for those ornamental fishes but the truth is that the unnecessary work that comes with using soft water is not just worth it.

Below are some other challenges with aquarium fish and softened water:

  • Maintaining the pH of soft water is a big problem. Because of their low concentration of calcium carbonate which is a natural water buffer, their pH easily fluctuates. If the pH goes below 7, this is very dangerous as it can kill or at least make your fishes go sick. This means that you have to always monitor the pH of the water to make sure it is safe and if it is not, you have to quickly do something about it and this can be very stressful.
  • Another problem is that if your fishes are the type that thrives well in soft water regions and the water you have readily is hard water, changing that your hard water to soft water is very expensive. Reverse-osmosis filters are what are used to carry out this process and they are really expensive.
  • I know that you may say that domestic water filters are readily available and you can easily use this. Let me break it to you yes they can soften water but this water cannot be used in an aquarium. Why you may ask. The reason they can’t be used is that they only replace lime scale-forming minerals with minerals that don’t form limescale. This water may be ok to use for washing, but for an aquarium, it is so not useable.
  • Remember how important good bacterial colonies which usually love to multiply in your tank filter are, in soft water they don’t do well. They prefer hard and alkaline water. Do you know what this means? It means that if you use soft water in your tank, you are going to have a lot of ammonia accumulating in your tank and this can lead to the death of your fishes.

Other Frequently Asked Questions

How do you soften water naturally?

Most fish species cannot survive in hard water. Softening water naturally can be effective and has much lower associated costs than buying a water softening system, but they also require a huge amount of time and elbow grease.

What fish can live in tap water?

Tap water is often chlorinated and in consequence, can lead to your fish consuming metals. The chlorine will subsequently kill the healthy bacteria that a freshwater aquarium needs to survive. This can then lead to an ammonia spike in the aquarium.

To make tap water safe for fish, it can be pre-treated with a liquid water conditioner. This helps to instantly detoxify the fish tank of both chlorine and chloramine and leads to water changes by binding up any heavy metals.

Is boiled water safe for fish?

Using boiled water for fish in your aquarium does not guarantee to remove the chlorine content. It will be beneficial in helping collect together any non-volatile mineral content. A more suitable approach will be to ensure your aquarium water is at an appropriate temperature, then attach a good tap water conditioner to it.

If you are using a good water conditioner then the chlorine and chloramines in your water will be removed after about 10 – 15 minutes of adding the conditioner

In conclusion, soft water can be used in your aquarium, but it is not advisable except your fishes are the type that typically survives well in this kind of water. Even though they do well in it, you will still have to stress yourself maintaining the tank as you can see above, this water comes with a lot of challenges.