I had no idea what water hardness was when I started my hobby. It was a concept I had no idea about. This was probably the reason that a few of my fish lost their lives. If you are a beginner, like me, I will teach you everything you need to know about reducing GH in your aquarium.
This guide will be very detailed. I will touch on several important topics related to water hardness.
Buckle up! It will be a long journey.
How To Reduce General Hardness (GH) In An Aquarium?
For many reasons, it is essential to reduce the aquarium’s water hardness. Natural elements such as peat moss and driftwood are the most popular. Sometimes, however, we have to rely on alternative options such as reverse osmosis or water softening pillows.
Let’s take a closer look!
Peat Moss Filters
For aquariums that have a high level of hardness, peat moss is my favorite choice. Peat moss helps reduce hardness by binding calcium and magnesium ions. This is called chelation.
Peat moss not only demineralizes the water but also releases tannins and gallic acids in the water. This exchange lowers both pH and KH as the acid neutralizes water’s carbonate and bicarbonate ions.
You can buy peat moss online or offline. However, you will need to prepare it before you can use it.
The water may turn brown from contaminants or pathogens in peat moss. Boil the water vigorously until it turns brown.
You can soak peatmoss in water for 3-4 hours if you have the time.
There are three main ways that peat moss can be used to soften water in aquariums.
They are:
- Use an additional outside container
- Use inside an aquarium filter
- Use as a substrate layer
Using in an extra outside container
This is the easiest way to use peat moss. It involves softening some tap water and then pouring it into the tank. However, you will still need to boil the moss or soak it before using it.
You will need small mesh bags for this technique. The peat mosh should be added to the mesh bags as tight as possible. Place the bags in a container with water.
You should test the pH and DGH value regularly – I would do this once every 10 hours – until your desired hardness is reached.
This method is not for everyone. A sudden, drastic change in the environment can cause more damage to your fish than incorrect water parameters.
In tanks that are already established, you can add softened water each week while changing the water.
Using inside the aquarium filter
This is a simple but effective way to soften tank water. To use peat moss as filter media, simply place a bag of peat moss inside the filter. You can prepare moss the same way as I did.
After boiling the peatmoss, let it cool completely before you add it to your filter. It is important not to alter the water temperature.
According to my research, placing the moss bags between charcoal media and the filter pad will increase effectiveness and yield better results.
Using as a substrate layer
This method takes a little more effort than the previous two. You don’t have to stuff peatmoss in mesh bags. Instead, spread the peat moss over the tank’s bottom and cover with another layer of substrate, such as sand or gravel.
Because peat moss has a light and fluffy texture, it is easy to move. It can be easily moved by water and curious fish. An additional layer of gravel, sand or sand helps to prevent anaerobic pockets from forming that promote the growth of harmful bacteria.
This method does have one drawback, so I chose the two previously mentioned. The substrate absorbs minerals and will brown water, even if you have previously boiled the water and cleaned the moss.
You can skip this method if brown is not your style.
Pros Of Using Peat Moss
- Water softener natural
- Economic options
- It is simple to use and very effective
Cons Of Using Peat Moss
- It is possible for the water to turn brown
- Water with a high GH value is not very efficient
Reverse Osmosis (RO/DI)
You might consider a RO/DI (Reverse Osmosis) unit if your tank’s water hardness is increasing more frequently. While DIY methods are possible, a RO/DI system will make your life easier and save you time in the long-term.
The membrane filter unit filters the water to ensure 100% purity. RO water is completely pure and has no hardness. This makes it unsuitable for aquariums. However, RO water can be mixed with tap water or remineralized by adding minerals.
While an RO/DI unit will cost more upfront, it will pay off in the long-term. We recommend purchasing one if you have a large tank.
This video will show you how to use the RO system in your aquarium to reduce hardness.
Pros Of Using RO/DI Units
- Permanent solution
- A long-term economical choice
- Provides zero hardness
Cons Of Using RO/DI Units
- High initial cost
- Bulky built
Driftwood
Driftwood is a great way to kill two birds with one! Driftwood helps lower the water hardness. It gives your tank a stunning appearance.
Driftwood is just like peat moss in that it works its magic. It creates acids and tannins which neutralize carbonate compounds in the tank.
Driftwood can also be used to reduce the pH level of water to make it slightly acidic, which is what most people prefer. It also promotes the growth of beneficial bacteria within the tank.
Malaysian driftwood is the most effective because it has high levels of tannin. You can also use other tannin-producing leaves such as the Indian almond leaves if you don’t like driftwoods.
Driftwood is easily available in stores or can be collected from the wild. Since driftwood is already pre-treated and prepared by manufacturers, I would choose the first option.
It doesn’t mean that you can just place it in the tank immediately after purchasing it. It will still need to be cleaned thoroughly and sterilized before it can be safely placed inside the tank.
Driftwoods have different levels of tannins. Some tannins are released even after six months. Others only release them for a few weeks.
If you feel that the water is becoming harder even though there is driftwood in it, it might be time to replace it.
This article might interest you if you want to learn how to treat driftwood so it is safe for your fish.
Pros Of Using Driftwoods
- Reduces water hardness slowly
- Natural and safe
- Fish immunity is increased by Tannins
- Prevent fungal infections
Cons Of Using Driftwoods
- Preparation can be a difficult and long process
- Water will turn brown
- If not properly treated, parasites can be leaked into the tank.
Water Softening Pillows
Water softening pillows can be purchased as chemical filtration media. They reduce water’s hardness. These pillows are made up of ion exchange resins, which replace calcium, magnesium, or other water-soluble heavy metals ions.
These work by decreasing the calcium and magnesium levels in the water.
These ion exchange resins are my favorite because they don’t cause any harm to your fish or aquatic plants. These pillows can also be used to remove white crusty deposits from the tank’s surface.
These pillows become less effective over time so you need to keep them topped up. Recharging them is easy.
Simply soak the pillows in salt water solution for at least 2 hours.
These are best for tanks smaller than 30 gallons. You might consider other options for larger tanks. You will have to recharge the pillows every other day.
Pros Of Using Water Softening Pillows
- Rechargeable and reusable
- It doesn’t cost much
- Useful for filter media
- Small tanks are well-suited for this product
Cons Of Using Water Softening Pillows
- It can be tiring to recharge.
- It is not a natural way to do it.
- Not suitable for big tanks
Rainwater
Rainwater is the best way to lower your tank’s GH. It’s also the cheapest method, Rainwater is generally soft, so you can always test its GH and KH.
Rainwater is not always available in all regions. If you can arrange to collect rainwater for dry days, that would be a great idea.
It could be, for example, a large container that is clean and has a lid. The lid can be removed and the water can be let in when it rains.
You can mix rainwater with tap water if it is too soft for a fish tank.
These are some steps you can take to make sure your rainwater is safe.
You should keep your rainwater collection container clean and sterilized at all times.
It would be best to label the container as ‘food-grade’ so that it doesn’t leach chemicals in the water.
Choose a rainwater harvesting system that does not contaminate the water.
If you live in an area with high levels of pollution or near industrial areas, skip this step.
Pros Of Using Rainwater
- This is a cost-effective method
- 100% natural yet effective method
- Sustainable approach
Cons of Using Rainwater
- It takes comparatively more effort
- In all areas, not possible
- It is not practical all year
Distilled Water
Distilled water is last on this list, but it’s still very effective. If you have the time and desire to make your own distilled water, you can either buy it or make your own.
Water is purified by distillation. The water is first boiled to make vapor. The steam is collected and condensed to make distilled water.
Distilled water, as you probably know by now is free from any minerals. Pure water is created when the vapor evaporates.
You should still dilute the distilled water with rainwater until it reaches desired GH levels, before adding it to your tank.
What is water hardness?
Chemistry does not always need to be complicated. Water hardness is the measure of the amount of dissolved minerals present in water. Calcium, magnesium, and carbonate are the main minerals responsible for hardening water.
It is a natural law that the more minerals in water, the more difficult it will be.
What’s The Difference Between General Hardness And Carbonate Hardness?
General hardness (GH), measures the amount of calcium and magnesium ions present in water. Carbonate hardness, on the other hand (KH), measures the concentrations of free carbonate and carbonate ions.
We usually use carbonate hardness to determine water’s pH. Water hardness is not a general term. Don’t get confused!
This table will help you understand the situation better:
| General Hardness | Carbonate Hardness (KH) | |
| Units for measurement | Grades of hardness (dGH), or parts per million, | Carbonate hardness in degrees (dKH), or parts per million (ppm). |
| Equivalent to 1 degree | 1 dGH = 10 mg of calcium oxide/liter of water 17.84 ppm | 1 dKH = 17.86mg calcium carbonate/liter of water, or 1 dKH= 17.86 ppm |
Pet fish can be raised in captivity and are biologically used to the water conditions of their natural habitats. Their fragile lives can be abruptly cut short if they are exposed to the wrong environment.
Depending on the source of the water, the general hardness ranges from 10 to 500 mg/l.
For example, American cichlids such as angelfish or oscars are bred in Amazonian river basins with GH values as low as 10mg/L.
Peacocks and mbunas, on the other hand come from rift lakes, where the GH can reach as high as 500 mg/l.
You can see how crucial it is to have the water’s GH values correct.
These tables will help you understand how hard water should be for different tank configurations.
| Water Hardness | General Hardness |
| Very soft | 0-4 dGH |
| Soft | 4-8 dGH |
| Very difficult | 8-12 dGH |
| Moderately difficult | 12-18 dGH |
| Hard | 18-30 dGH |
| Very hard | >30 dGH |
| Tank Setup | General Hardness |
| Tropical Fish Tank | 4-11 dGH |
| Cichlid Tank | 12-20 dGH |
| Shrimp Tank | 4-8 dGH |
| Marine Tank | 8-12 dGH |
| Brackish Tank | 12-20 dGH |
| Axolotl Tank | 7-14 dGH |
| Fish Pond | 4-11 dGH |
| Plantted Tank | 3-8 dGH |
How Does Water Become Hard?
Nature’s water flows through many rocks, including limestone and dolomite. Mineral concentrations can also be found in soil. When water passes through these surfaces, minerals slowly leach into water, causing water concentration to rise.
The location of your tap water and the natural route it takes to reach you will determine the hardness. These minerals are not harmful to mammals but can be dangerous for fish.
How Is General Hardness Measured?
Technology has made it possible to measure the hardness of water in your tank from your own home. There are many ready-to-use testing kits available.
This API Test Kit measures general and carbonate hardness.
Because they are more reliable, we prefer liquid-based tests to strips.
Why should you soften aquarium water?
Aquarium water doesn’t have to be always softened. Some fish can thrive in hard water. If you have fish that require soft water, it is important to not expose them to the wrong water parameters. They will not only survive and thrive in soft water, but they can also reproduce easily. It helps avoid lime deposits and hard water stains, and protects equipment from rusting.
Allows Fish To Thrive
Some fish species, such as angelfish, gouramis and gouramis require soft water in order to thrive, including barbs and oscars. Simply put, their bodies are not designed to absorb all minerals in the water.
These fish will become extremely stressed if they are constantly exposed to hard water. This will lead to decreased immunity and stunted growth. It also makes them more susceptible to the opportunistic pathogens in their tank, which are just waiting for the right moment.
Encourages breeding
Even if the soft water species can survive in hard water conditions, they won’t breed. Fish will follow their instincts and avoid breeding in unfavorable environments.
You can encourage the breeding of soft water species by lowering the tank’s hardness and increasing acidity. To increase breeding opportunities, you can conduct a large water change and provide protein-rich food.
If you’re transferring the breeding pair from one tank to another, be sure to adjust them slowly to the new environment to avoid shock and stress.
Prevents hard water stains and limescale deposits
It is difficult to remove hard water stains from a tank, regardless of whether it is an acrylic tank or a glass tank. You will also end up with ugly scratches and a cloudy view when you try to remove limescale buildups.
These problems won’t occur with soft water. Let me rest my case!
Protects equipment from malfunctioning
Your tank equipment is more susceptible to corrosion and limescale buildup in hard water. This can lead to frequent malfunctions and a short life expectancy. Hard water can cause damage to powerheads, filters and air pumps.
Soft water is a must for proper operation and long-term durability of tank equipment.
But not all fish are created equal. Some fish thrive in hard water, while others struggle.
Let’s take a look at the fish that can thrive in both soft and hard water.
Fish that thrive in soft water
| Cory catfish | 3-10 dGH |
| Angelfish | 3-8 dGH |
| Tetras | 2-10 dGH |
| Gouramis (some) | 5-10 dGH |
| Rasboras (some). | 4-12 dGH |
| Ram Cichlids | 3-6 dGH |
| Discourse | 3-8 dGH |
| Apistogramma dwarf cichlids | 3-12 dGH |
Fish that thrive in hard water
| African cichlids | 11-22 dGH |
| Guppies | 8-12 dGH |
| Mono fish | 8-14 dGH |
| Archerfish | 20-30 dGH |
| Swordtails | 12-35 dGH |
| Mollies | 15-30 dGH |
| Platies | 10-28 dGH |
| Paradise fish | 5-30 dGH |
Final Words: How To Lower GH In Your Aquarium?
The water’s general hardness is the amount of calcium and magnesium ions in the water. Some fish, such as guppies or cichlids, thrive in hard water. Others rely on soft waters for survival.
It is easy to lower the GH level in your aquarium. Peat moss filters are the most popular method. This is what I use.
You also have the option of reverse osmosis and water softening pillows, rainwater, distilled water, and driftwood.