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How To Remineralize RO Water For Aquarium?

Fish and other aquatic organisms have this amazing ability to adapt in the face of many different conditions and environments.

However, most people want their fish tanks filled with clean water for the better overall growth of the tank mates.

RO (Reverse Osmosis) filters are capable of removing all minerals from tap water as well as purifying any harmful compounds it may contain, but it is not suitable to have all the water with no minerals as, without them, your guppies, bettas, and shrimps could get into severe danger.

Therefore, you need to remineralize your tank water.

So, in this article, we will guide you on How To Remineralize RO Water for Aquarium.

We will discuss about the method of supplementing beneficial minerals to the water, how reverse osmosis runs, and also why RO water is the best prospect for your aquarium.

How To Remineralize RO Water For Aquarium?


You could be using RO water for your aquarium, but there is one extra step if you are. To attain the best possible living conditions and health benefits in an environment with no minerals or trace elements-it must undergo purification.

An additional purification process is called re-introduction, where certain compounds are introduced at specific times, providing several benefits for aquatic life, including maintaining ideal living conditions like pH levels on their own.

Maintaining Right Water Parameters


The water parameters that you will need to take into consideration when caring for your aquarium are pH, total dissolved solids (TDS), carbonate hardness, and general hardiness. To create the best possible aquatic environment, it is important to keep these four natural balances in check and ensure they don’t exceed the set limits.

The Total Dissolved Solids must be 390 ppm, whereas pH should be neutral at 7-7.5 pH; alkaline levels range from 8-9 kH on average, while the general hardness should be around 10 GH.

Best Way To Remineralize RO Water

The science of remineralization is a complicated process that depends on factors such as the percentage and type of RO water you are using.

Ever wonder what you want to do to achieve these water conditions?

Well, it’s all thanks to an easy recipe. All you need is 5 milliliters (1 cap full) of water conditioner and 1 teaspoon baking soda mixed together with ¼ teaspoon acid buffer for every 50 gallons of RO water.

Rinsing and washing out the tank will help you get a good start on remineralization. Spin it with tap water before filling up, or use RO (reverse osmosis) for better results!

Ensure to rinse off all residue so that no detergents are left behind, which could cloud your tank after filling the tank.

There are many ways to restore your fish tank’s water, but there is still hope if you don’t have access to the materials needed for the solutions mentioned above.

A mixture of calcium chloride, Epsom salt with baking soda will make an excellent alternative and provide all essential minerals that may otherwise be lacking in a poor quality RO drinking supply.

It is important to ensure that your aquarium water has the desired pH level for its inhabitants.

As such, we recommend adding remineralizing cartridges if you are experiencing higher than expected alkalinity levels after a RO process as it may be due in part to removing all of the minerals when Filtered Water From An Reverse Osmosis System is being used instead.

One of the best ways to keep your freshwater tank healthy is by using Seachem Equilibrium. It functions to achieve an optimal mineral and electrolyte balance for aquariums and maintain stable carbonate hardness levels that will make sure all fish are happy in their new home.

Also Read: Pink Orchid Betta Fish for Your Aquarium

Why Is It Important To Remineralize RO Water?

RO water is purer than bottled, tap, and lake waters because there are no residual chemicals or minerals. The reverse osmosis process also neutralizes the pH of its drinking supply to make sure you have an absolutely blank slate for all future concoctions!

The fish in our tanks need different water qualities. Some of them require alkaline or salt-heavy waters, and others prefer to live in pH-neutral conditions with less sodium chloride (salt).

Remineralization is a perfect solution to create the ideal living environment for your fish. It’s done by adding certain compounds and chemicals, like baking soda which primes water to best suit their needs so they can thrive in it.

Why You Should Use RO Water In Your Aquarium?

A common misconception about RO water is that it will harm your aquarium. The method of remineralization and choosing particular buffers may sound intimidating, but don’t let this put you off from using RO for all purposes in an aquarium!

The reverse osmosis process takes all the harmful substances from your water, leaving it clean and pure. It removes harsh chemicals like chlorine gas as well as organic ones such as pesticides or even arsenic.

Therefore, you must build neutral water conditions. RO water also eliminates:

Water Hardness


Hard water stains are a common problem for homeowners. When the calcium and magnesium in your household’s drinking tap come from an outside source, it creates more of these deposits that can quickly build up on faucets or sinks until they’re almost impossible to remove without professional help.

The hardness of the water shouldn’t be a concern to humans, but it can wreak havoc on fish and other aquatic life.

Hard water is hard on fish, which limits the variety you can introduce to your tank. However, some community members like guppies and archers will live well in these conditions, but most others won’t stay for long before they’re gone!

Some fish thrive in freshwater, but not all.

Freshwater and tropical environments have different temperaments because of the chemicals within them that are needed for survival.

The reverse osmosis system is the perfect solution for anyone who needs to keep tropical fish. Once installed, it makes water neutral and removes all hardness so you can control how much your fish need in their environment with precision!


When oxygen and nitrogen combine, we get Nitrates. These can be found in large quantities throughout our water supply, even though they don’t significantly affect human health.

The problem is that these harmless-looking compounds are actually disruptive to marine life when present at high levels; it’s just hard for us humans to see this.

Your fish are quite sensitive to nitrates, and as the content of these compounds in your water increases, it will promote algal growth. This process quickly spreads throughout an aquarium- something you want to be mindful about if you have any precious species living there.

Aquarium fish are incredibly sensitive to high levels of nitrate.

At 100 ppm, even the most resilient aquarium inhabitants will likely show symptoms like poor health and vitality. This is a disaster for the young fry if you have any present in your tank.

Most people think that a saltwater aquarium needs to have high nitrate levels, but this isn’t true. As long as you keep the water clean and your fish happy with nutritious food (and corals!), then everything will be fine! 

  • Freshwater aquariums typically see between 0-40 parts per million of Nitrates
  • While Reef systems can go down below 5 ppm for their ecosystem not to be disturbed when set up properly.
  • Saltwater aquariums can go from 10 to 40 ppm

You might think that the levels of nitrates in your aquarium are low, but even a sudden increase can have damaging effects on these organisms. 

Sea apples won’t be able to handle it either, so they’re not worth using as an aquarium substrate since all those little bugs need constant care and cleaning, just like we do with land plants.

Fish produce nitrates as a waste byproduct, and this is what causes their levels to increase. RO water will show you the most about these changes, so it’s important for people who care about fish to always buy their drinking water in an aesthetic system like Reusable Drinking Water Bottles where they can get rid of harmful chemicals altogether!

When your aquarium begins with almost no nitrates, this waste release doesn’t instantly result in eminent increased levels of nitrate; but instead, the nitrates slowly build-up, and they will be eliminated once again from your water tank when you change the water regularly.

To further remove or eliminate nitrates from your aquarium, you can add mangrove plants which will help by clearing out the nitrates and removing bacteria that live on the rocks. 


The most common contaminants in well and tap water are silicates. Pets with sandy substrates constantly leach out these unwanted particles into your tank.

These contaminants can take over your aquarium in a short period of time and start producing silica algae in the tank.

Silica algae also called gravel algae and a serious problem in aquariums. This brown film will coat the floor of your tank with its rampant growth within no time at all.

Furthermore, the film stops the light from entering your water tank and decreases the oxygen levels.

The worst enemy of your aquarium could be the algae. Not only do they deplete oxygen, but some even have a carnivorous effect on corals and start populating at base level to consume it from top-downward. The coral’s skeleton is damaged as well with time; its health will gradually decline.

The most reliable method to get rid of silicates is by applying reserve osmosis. These contaminants cannot pass through the RO membrane barrier, so they won’t be equipped to interact and injure your coral in any way.


The high phosphate content in your tank is a problem because it promotes the growth of algae. The green algal cover will quickly take over and suffocate all life in an aquarium, drastically reducing oxygen levels to dangerous levels for fish to survive in.

Tap water can be perfectly clean and still contain excessive amounts of phosphate, which will harm your coral. Phosphates are found in drinking water and fish waste from uneaten food or decaying plants near the bottom of tanks.

Tap water generally ranges from 1 – 10 ppm. Fish waste and uneaten food also increase the amount of this phosphate within your aquarium, and if more than 0.2 ppm phosphate is present in your fish tank, then it will be too much for most coral communities.

Since there is no way of cleaning out phosphates from your tank once they are in the aquarium, it’s best, to begin with, RO water. Giving your fish low phosphate levels will ensure minimal algal growth and keep your aquariums clear of algae.

Maintaining an optimal level for zero or close-to-zero nutrient production makes sure minerals stay within their ideal ranges, which helps prevent any negative side effects on the health of your tank and tank mates.

Balanced Water Conditions

When designing living conditions for your fish, it is best to use RO water which has no flavor or color. This way, you can create an environment where they will grow healthily and thrive in this neutral setting.

RO water is the best way to offer your fish a stable tank regardless of how good or bad water running through pipes may be.

This makes it important for those who live in areas with fluctuating natural resources, such as rainwater which can cause salt levels and mineral content fluctuations over time.

With RO units on hand, you’ll never have any worries when monitoring pH balances between hard waters and salty mineral water.

Fish are sensitive creatures that require unique combinations of minerals and pH to live happy, healthy lives.

Even slight diversions from these parameters can wreak havoc on an aquarium’s inhabitants; many seasoned aquarists will tell you tales about how the smallest imbalances in water tank conditions were plaguing their marine life, destroying everything within it.

For instance, the perfect water for your angelfish is the one that has a neutral pH and low hardness. If you stay in a place with hard waters or want to use well-water, it can cause many problems with your angelfish, or your fish won’t live longer.

Livebearers are an excellent choice for hard water fish lovers.

Livebearing species such as platies and guppies prefer alkaline conditions with a pH level of 8 or higher.


It is always best to use the blank RO water because you can then make any required adjustments easily and get an accurate water parameter that you need where your fishes will thrive.

Adding acidic buffers or mineralized solutions to your fish tank is easy with the help of 100% pure water. The results are predictable and can be tweaked for any preference that your fish may require.

Fishkeeping Expert
Fishkeeping Expert
With years of collective fishkeeping knowledge, we are pleased to share the tank maintenance tips and fish care advice we've picked up along the way. Fishkeeping Expert is home to all fishkeeping tutorials and guides that will help you keep your fish healthy.


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