How to Lower GH in a Freshwater Aquarium

How to Lower GH in a Freshwater Aquarium

Water hardness, might or might not affect you depending on where you live. It could also adversely affect the lives in your aquarium if left unattended to, and so you might want to make yourself with some of the methods that you could use to soften hard water.

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What is hard water?

General hardness, commonly known as water hardness if abbreviated as GH. It is simply a measure of the concentration of naturally occurring salts that have been dissolved in water, particularly magnesium and calcium. 

Water with high GH is considered to be hard and that with low GH is considered soft. Therefore, hard water contains a lot of magnesium and calcium whereas soft water has very little or none of these salts.

Your aquarium’s GH totally relies on your source of water. 

Difference between KH and GH

A lot of people often confuse these two; KH (carbonate hardness) and GH (general hardness). Even though both have the phrase hardness, they determine totally different water parameters.

GH is a measure of calcium and magnesium that is dissolved in your water, while KH is a measure of bicarbonates and carbonates dissolved in the water.

KH and GH, although different, still go hand in hand in nature. This is to say that if a certain waterway such as a river has a high GH, then it also definitely has a high KH.

Tap water is, however, far from being natural.  It is possible for tap water to have a really high GH and an extremely low KH. Therefore, a high GH doesn’t essentially imply that the KH is high as well.

How to determine the water in your aquarium is hard or soft

There are a couple of ways of telling whether or not your aquarium’s water is hard. One of the most direct and easiest ways is by checking for scaling in kettles, or scum in your bathtub, sinks, or showerhead. If you notice any white deposits, then it is likely that you are using hard water.

A more accurate way is taking a scientific approach; use a test strip. Test strips are available for just a few dollars. They will leave you with an accurate indication of just how hard the water you are using is by matching the color on the test strip to a provided chart.

You could, alternatively, contact your local water supply company. They should tell you whether the water that they are supplying is soft or hard. 

You can also find published maps online that will provide you with information regarding the hardness or softness of the water in your region.

How to lower your aquarium’s GH

The methods that can be used to lower your aquarium’s GH or other make hard water soft are not that difficult to execute and they can indeed make a huge difference in the comfort and safety of your fish. An important thing to always bear in mind, however, is that adjusting your aquarium’s hardness level should be a gradual process. Huge and drastic GH changes in your aquarium will only result in serious problems for its inhabitants.

That said, let us now take a look at some of the methods that can be used to lower GH in a freshwater aquarium:


Applying reverse osmosis (RO)


This is one of the most effective ways of lowering GH. It eliminates about 95 to 99 percent of minerals, chemicals, as well as other dissolved substances leaving behind water that is clean and pure. 

The best part is that no harmful products or chemicals are used here. Reverse osmosis works by pushing the hard water through a somewhat porous material at very high pressure. The filter only allows for the passage of clean water and traps any contaminants that were contained in your water.

Given that reverse osmosis could be a slow process, it is advisable to process small bits at a time, and store the excess in a huge Rubbermaid for use next time. At times you might find that your RO water needs to be mixed with tap water for there to be a balance between softness and hardness. This helps with balancing your aquarium’s pH levels. You could, alternatively, add special salt mixtures to your RO water.


Use of water softening pillows


Water softener pillows utilize some sort of chemical filtration medium, usually ionized resin that lowers the water’s general hardness. They decrease the magnesium and calcium levels but raise the levels of sodium in your fish tank water. The filtration media can be re-used and re-charged through submerging it in a salt solution for a while.

Water softening pillows work best for smaller tanks (less than 25 gallons). This does not mean that they cannot be used for the larger tanks. You will just have to recharge it more often when used in a huge tank. 

The major downside of using water softening pillows is that in as much as they lower your aquarium’s GH levels, they increase its sodium levels. In some cases, this could turn out to be toxic for your aqua-pets. It is like a trade-off, exchanging one impurity for another.

Nonetheless, it is still a good option if have money and space.


Using peat moss


You can also use peat to lower your aquarium’s GH. Peat binds magnesium and calcium ions together whilst releasing tannic and gallic acid into the water. These acids attack and break down the bicarbonates in your fish tank, further decreasing your water’s carbonate levels as well as its pH.

There is more than one way of using peat moss in your fish tank:

  1. Placing the peat moss inside your fish tank filter. This ensures that there is a continuous stream of water always flowing over the peat, which in turn maximizes its effectiveness.
  2. Adding it to a bucket with water for a minimum period of two weeks before use. Once it’s time to use the water that you’ve been treating, just strain it through a tiny sieve and it will be ready for use in your fish tank.
  3. Adding the peat moss to a pillowcase and then directly submerging it into your aquarium. You, however, have to ensure that your aquarium is properly aerated to prevent a drop in the levels of oxygen.

Whichever method you go for, just ensure that your peat is sterilized (boiling it for some minutes). In addition, you should only purchase untreated peat that has no additives.

One downside of using peat moss is that could make your aquarium water brown for a bit. This should, however, not worry you. The brownness is as a result of the tannins being released by your peat. It might look unattractive but it is totally harmless and will disappear after a while.


Use of driftwood


Driftwood works similarly to peat moss. It is quite effective when it comes to lowering your aquarium’s GH.

It is advisable to purchase driftwood either online or from one of your local fish stores. This helps to prevent any invasive species or parasites from invading your fish tank. You can, however, still decide to boil your purchased driftwood just to ensure that everything is clean.

If you immediately immerse the driftwood into your fish tank, your aquarium water will turn to a brown color. Just like peat, this is simply tannins being released by the driftwood. Even though it is harmless, it is still something that you may want to avoid. One way to avoid this discoloration is by soaking the driftwood for a few weeks before using it.

After the driftwood into your aquarium, it is important to ensure that the water is moving and properly aerated. Additionally, during the first few weeks, it is advisable to watch out for any growths on the wood like slime algae. Regular and frequent water changes could prevent this.


Switching to rainwater


This is the best option for anyone who has a low budget. But this will only work if you reside in an area with good air quality to ensure that your rainwater is chemical-free. In addition, your storage containers as well as water capture system need to be clean and disinfected, as well as being food grade to prevent any chemicals from leaching into your aquarium water.

Since rainwater is extremely soft, you might have to mix it with tap water or special aquarium salts to raise the GH and KH levels to suitable levels.


For freshwater fish, having a low GH in your aquarium is very important. High GH levels in your aquarium water can stress your fish and at times, if things get worse, your fish could die. That is precisely why freshwater fish cannot survive in salt water (water with a lot of dissolved salts).

It is advisable to always test for your tap water’s GH levels before using it in your aquarium.


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