How to Reduce Water Hardness in Aquariums? Easy Tips

How does hard water affect fishkeeping? Is it worthwhile to investigate how to soften aquarium water?

To reduce water hardness in a tank, you can use reverse osmosis (RO) or distilled water, add peat moss or driftwood to the tank, or use a commercial water softener. It is important to monitor the water hardness levels regularly and make adjustments as needed to maintain a stable and healthy environment for your fish.

In this post, we’ll look at the most effective strategies to soften aquarium water. Keep in mind, though, that water hardness, like all tank characteristics, is not an absolute value that you should strive for.

GH and KH in an Aquarium

Water hardness in an aquarium is caused by the deposition of mineral deposits in the water. This is due to the biological process that keeps pet fish and plants alive. As living creatures, they ingest and exhale chemicals, which are subsequently discharged into their natural habitat, water. These chemicals and substances accumulate in the water over time.

GH and KH in an Aquarium

Water hardness is sometimes known as general hardness. The calcium and magnesium concentrations in water are used to calculate general hardness. A high concentration of two minerals in water results in a high GH, whereas a low concentration results in a low GH. Minerals are important for aquarium fish, but too much might be detrimental.

KH, which measures calcium bicarbonate levels, is another standard for assessing water hardness. When we talk about water hardness, we usually refer to GH and KH. It is critical to assess the hardness of your aquarium’s water and adjust the GH and KH accordingly. If it is too high, the hardness of the water must be lowered. Here are the steps for reducing water hardness in aquariums.

Related Post: Is Hard Water Bad For Fish?

Ways to Reduce Water Hardness

It is simpler to deal with changes in water hardness rather than starting from scratch, thus it is critical to evaluate it frequently. Testing strips are affordable and effective; electronic testers, which cost a little more, are also available.

The methods for softening hard water are simple and may make a significant difference in the safety and comfort of your fish. Just keep in mind that altering the hardness level in an active aquarium should be done gradually. Any significant changes in hardness rating might create major issues for your fish, resulting in disease or worse.

Reverse Osmosis

This method is ideal if you need to reduce the hardness of your water after each water change. The RO system cleans the water by removing minerals and impurities. However, the system has the potential to make the water overly soft, rendering it unsuitable for some fish species.

RO works by applying high pressure to hard water and pushing it through a slightly permeable medium. The filter removes any pollutants, enabling only pure water to flow through.

What is Reverse Osmosis Water

Because RO may be a long process, it’s best to process batches at a time, keeping surplus in a big Rubbermaid until you’re ready to use it again. To achieve a balance of hardness and softness, you may need to blend RO water with conventional tap water. This can assist in balancing the PH levels in an aquarium. You may also add specialized salt mixes to the RO water.

Using Water Softening Pillows

If you’re wondering what a water-softening cushion is, I am here to assist. Water Softener Pillows employ a chemical filter media, often an ionized resin, to lessen the overall hardness of your aquarium water. They lower the calcium and magnesium levels in your aquarium water while increasing the sodium levels.

By soaking the medium in a salt solution over a length of time, the medium may typically be reused and recharged.

Using Water Softening Pillows

Most water-softening pillows are somewhat successful in reducing GH and may be added to your current water filter. They work best in smaller aquariums of around 25 gallons, but they may be used in bigger tanks as well; they simply need to be recharged more frequently.

One disadvantage of a water-softening pillow is that it lowers GH levels while increasing salt levels, which might be harmful to your fish in some cases. Substituting one contaminant for another is a trade-off. If you have the room and money, a RO unit is still a better investment.

Related Post: How to Soften Fish Tank Water Naturally?

Using Distilled Water

Distilled water is clean water that requires some hardening if it is to be used in your tank. Water is converted into steam during the distillation process. Impurities such as minerals and salt are not present in heated water. That’s why you’d need to remineralize it or mix it with tap water. In this scenario, though, you may control the amount of hardness required.

Using Distilled Water

Peat Moss Filters

When used as a filter medium, peat moss decreases water hardness by binding calcium and magnesium ions. This is known as chelation, and it softens aquarium water by demineralizing it

Peat releases tannins and gallic acid throughout the process. This exchange reduces KH and pH levels by neutralizing carbonate and bicarbonate ions in the water.

Peat Moss Filters

Boil peat moss for 2-3 minutes before using it as a filter medium. This eliminates the possibility of encountering hitchhiking parasites or other pollutants. To prevent excessive yellowing of tank water, soak peat in clean water after boiling.


Using driftwood to alleviate water hardness in aquariums is nearly the same as using peat. However, one must ensure that it does not include creatures or parasites that might infect the fish and harm the aquarium’s environment.


It is preferable to boil the driftwood to eliminate organisms before placing it in the aquarium. The risk of organisms surviving and growing after boiling the driftwood exists, thus you must monitor and study the driftwood on a regular basis.

Driftwood, like peat, emits tannic acid, which darkens the water. Aesthetically unappealing, yet absolutely safe to fish. Make sure that water is continually flowing in and out to wash away any remaining organisms in the driftwood. Overall, driftwood can raise GH and KH levels without the need for any technology.

The Bottom Line on How to Reduce Water Hardness in Aquariums?

To summarise, water hardness is critical in sustaining the health of your aquarium pet fish. You must always be aware of it and ensure that the appropriate degree of water hardness is maintained. It is not difficult to lower water hardness in aquariums, and the methods and techniques discussed above are as simple as they come.

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