Keeping fish in an aquarium is more difficult than many think. Keeping the fish in your aquarium healthy and happy comes down to a number of factors and providing the right environment for your fish is one of the most important.

The water in your aquarium is a vital part of that puzzle. The majority of aquarium problems are caused by water conditions, with the quality of the water impacting fish health and algae levels directly.

Here we take a closer look at what water is the right water for aquariums allowing you to create the perfect home for your finned friends.

What water do fish need?

Whilst in the wild, different types of fish make their home in both hard and soft water areas. The mineral content of hard water makes it unsuitable for use in aquariums.

Most aquarium fish species require soft water to survive and thrive, with the exception of marbled hatchetfish, discus, oscars, bettas, and paradise fish. Find out more about hard water-loving fish here.

It is recommended that you use softened hard water in an aquarium to ensure a stable pH level can be found and the best water conditions enjoyed.

Is my water hard or soft?

The hardness of water is measured in two ways, as general hardness and carbonate hardness. General hardness relates to the levels of dissolved calcium and magnesium in the water, while carbonate hardness looks at the amount of bicarbonate and carbonate ions.

To ensure optimum aquarium conditions, both the general hardness and the carbonate hardness must be at the right levels for your chosen fish species.

There are obvious visible signs that the water in your aquarium is hard. Just like with our tap water, hard water shows itself in many ways with the build-up of limescale evident on taps and in appliances. White residue or scaling will occur within the tank if the water is hard.

The easiest way to identify whether the water in your aquarium is hard or soft is to test it. It’s recommended that the water in aquariums is tested on a regular basis to ensure the best water conditions and to preserve fish health.

Test strips are easy to use, you simply dip the strip and wait for the colour change using the key to identify whether the water is soft or hard.

How should I soften water?

There are several simple methods that can be used to make your water soft enough and guarantee optimum comfort and safety for all the fish in your aquarium.

Reverse osmosis is the most effective option for transforming the hard water into a soft and stable environment. The Spruce Pets explains more about the process:

“Reverse osmosis is a filtration method which forces water through a series of filters, the last one being a semipermeable membrane that removes 90-99% of tap water impurities. The result is water that is free of minerals and other contaminants, such as chlorine, chloramines, pesticides, nitrates, phosphates, and heavy metals. The contaminants are physically too large and are thus unable to pass through the pores of the system.”

Water softening pillows can be added to reduce the general hardness of aquarium water, and are integrated into the water filter for extra ease. Those looking for a more natural way to improve water conditions can add peat moss to their aquarium filter or in the tank directly. Driftwood can also be placed in the tank for a similar effect.

Some have even turned to the rainwater method for an inexpensive way of stocking their tanks with soft water. Please note, this rainwater has to be collected from an area with excellent air quality and the resulting rainwater must be free from chemicals.