Reverse Osmosis Water For Betta Fish – What You Need To Know

Betta fish are the best for novice aquarists to keep as pets because they are among the most attractive and resilient freshwater species. However, you must remember your betta’s water needs to maintain its feeling and look its best. The best method is to use reverse osmosis water for betta fish. Let’s learn more about it with this post!

What Is Reverse Osmosis Water?

Reverse Osmosis Water system

Reverse osmosis is among the best techniques for filtering water. It purifies water by forcing it through a small filter, unlike chemical or carbon filtration systems that use specific materials to draw out or directly target the impurities in the water.

For usage in aquariums specifically, this cleaned water brings lots of benefits. Tap water can include levels of silicates, phosphates, and nitrates that can lead to undesired algal growths in your tank, and chlorine even kills freshwater fish. So reverse osmosis and salted reverse osmosis are the best options for freshwater fish keepers.

Why Should You Utilize Reverse Osmosis Water For Betta Fish?

Betta Fish

Reverse osmosis removes dissolved minerals, heavy metals, salts, and nitrates from the water, leaving unmatched purity a blank canvas, allowing you to design your aquarium habitat.

By eliminating up to 99% of the dissolved particles in water, reverse osmosis creates high-quality water free of contaminants, water hardness, and compounds like chlorine. This offers you a neutral setting to develop the optimal conditions for the betta fish to grow. 

Moreover, reverse osmosis enables you to control the water’s pH level, amount of salt, and mineral exposure. Simply put, aquarium stabilization is made simple using reverse osmosis.

Compounds That Reverse Osmosis Systems Filter Out

Reverse osmosis can be very useful as it can remove many substances from the water. Here are the harmful compounds that it can filter out.


algae in tank

Nitrogen and oxygen combine to form nitrates, a frequent substance in water supplies. Fish are significantly more susceptible to the nitrogen molecule than humans, who can tolerate it at low doses. Algae will increase all over the tank as nitrate levels rise.

Additionally, nitrates reduce the water’s oxygen content, which may be harmful to all fish’s health, not only your betta. Even hardy fish will experience stress and deterioration in health when the levels are above 100 ppm (parts per million). Fries and young fish are especially vulnerable to its hazard.


Phosphates accelerate algal development in tanks. If this is unmanaged, it can result in green, murky water and a reduction in the amount of oxygen in the water. Although phosphates may not directly kill the fish, a tank with an overabundance of algae will eventually lead to health issues for all occupants.

The growth of evil algae like the blue-green ones is toxic to your beloved betta fish and even destroys your complete aquarium ecosystem. This is because they produce Cyanobacteria, which is deadly for both animals and plants in the tank.



Silicate is a mineral that rainfall picks up as it travels through rock formations and underground aquifers. This compound is among the most frequent water pollutants since they make up around 90% of the crust of the earth. 

The silicates in a sandy substrate will quickly dissolve into the water when you use it as your fish tank substrate.

Due to the silicates’ high concentration in water, many tank owners struggle with the algae they create. Silica algae cause the brown film that covers the entire aquarium, also referred to as gravel algae, which grows across your rockbed. 

The algae development is made worse by having inadequate illumination and little oxygen in the tank.

Water Hardness

Water that has acquired excess magnesium and calcium during the hydrologic cycle of nature is referred to as hard water. The types of fish that can live in your aquarium are restricted by hard water. 

While many fish, including guppies, swordtails, etc., thrive in hard water settings, certain freshwater fish may have different personalities.

For example, angelfish and bettas are two tropical fish that can only survive in soft water. Reverse osmosis renders water soft and neutral, enabling you to regulate the precise hardness level you need. By doing this, you will have more options to choose from.

Frequently Asked Questions

What Amount Of Water Do Betta Fish Require?

Betta fish require a minimum of 5 gallons, ideally 10 gallons, of tank water since this allows your pet lots of room to swim and move around. Furthermore, maintenance is simpler because there is more opportunity for error with bigger tanks. Stable tank water parameters are also simpler to maintain.

What PH Level Do Betta Fish Prefer?

Between 6.5 and 7.5 is the appropriate pH range for betta fish. Bettas thrive in water that has a neutral pH. Fortunately, the majority of tap water has a pH close to these numbers, but ensure to test your water first using test strips.

Suppose the pH level is not right; the betta fish may experience shock, which is frequently lethal. Peat moss, driftwood, or pH-reducing solutions can all be used to reduce the pH of the water in your betta tank.

How Frequently Should Betta Tank Water Be Changed?

The stocking level and aquarium’s size will determine how frequently you should change your betta tank water. Suppose your tank is small and overcrowded; you might need to change the water once every few days. 

Meanwhile, a less frequent water change schedule, like once every two weeks, maybe adequate for bigger and understocked tanks.

Is Reverse Osmosis Water Suitable For Freshwater Aquariums?

Reverse osmosis water is a wonderful option for freshwater aquariums. Because reverse osmosis water lacks any discernible hardness, it is just too pure to be used in aquariums without adding some helpful salts and minerals. 

Without these additions, your fish won’t survive. The best option is to combine reverse osmosis water with regular tap water.

The Bottom Line

Now you know what benefits reverse osmosis water can bring. Using reverse osmosis water for betta fish is the best method to provide your fish with a suitable habitat to live in and develop. Keep in mind that the unsuitable kind of water can make your betta stressed, ill, and even die.