How To Use Reverse Osmosis In Your Aquarium

One of the prominent challenges for most aquarists or those who seek to take care of fishes is recreating the environment in which the fish used to live. Reverse osmosis systems could help you overcome this challenge.


A successful aquarium depends hugely on a solid foundation. A small number of compounds or elements could have a significant impact on your aquarium and your fish growth. For example, some could encourage algae growth within your aquarium, and some could stunt fish growth.
Most fishes from seawater or saltwater could live unless they are in the same environment as their natural habitat.

What Is Reverse Osmosis?

Having your water purifier gives you total control over the components you want to exist within your aquarium or tank. You can easily add and adjust it according to what your fish needs.

Reverse Osmosis

An example of a water purifier is the Reverse Osmosis (RO) system. RO is a process that purifies water and separates chemicals, pesticides, pharmaceuticals, and dissolved solids from the purified-water. These also include the removal of compounds and minerals. Water produced from a reverse osmosis system is an ideal starting point for your aquarium because it gives you a clear idea of its properties and components.

By subjecting your water to the RO system, you would not need to have your water checked. RO offers consistency, you know your water is purified, contaminants are removed(including magnesium and calcium that make the water hard), and the pH is neutral or slightly acidic. You can now easily adjust the water’s pH, hardness, and salt level,

Three Vital Parameters You Need To Monitor

First Parameter:

Importance of water hardness or General Hardness (GH)

Monitor your water GH level carefully, remember that there are fishes that prefer hard water than soft, and some that prefer the opposite. The amount or level of calcium and magnesium existing in your aquarium is the measure for your water GH level. The more of these elements present, the harder your water will be. Natural waters contain these minerals because some water passes through rocks that have these minerals in their composition(examples of these are gypsum and limestone). Water dissolves some of this and combines it with the overall water content. Different places have different minerals levels and different water hardness levels.

Some fishes can stand a certain level of hardness, but it could scientifically affect the breeding of the fishes. Fishes have osmoregulation ability, meaning they can modulate the salt and water concentration in their body. However, most fishes cannot grow well and reproduce in a place not similar to their natural habitat.

GH is where the fish gets electrolytes to grow their muscle and bone, and increase their immunity. It also helps the fish to digest food better.

Fishes GH preferences are different from one species to another, so make sure to check the GH level your fishes prefer.

Adjusting GH

The best way to decrease your GH water level is through reverse osmosis because it removes minerals or elements contributing to water hardness. (Namely Calcium and Magnesium)

You can bring back water hardness in your aquarium by simply adding stone or rocks rich in minerals. You can also try to put crushed corals because they are composed of calcium carbonate, and they can dissolve and combine with water over time. However, it is good to take note that these corals could also increase carbonate hardness(KH) and the pH level. You can also buy remineralizing buffers and add them to your aquarium to increase the GH level.

Second Parameter:

Importance of Carbonate Hardness/ Calcium Hardness(KH)

KH measures the level of carbonate and bicarbonate in water (some refer to this as tank alkalinity). Most people believe that KH is the main parameter one has to observe in maintaining an aquarium.

These work like a buffer for the pH of water and aquarium. A sudden change in pH does not sit well with most fishes and aquatic plants. These could significantly cause shock to your fishes and could even lead to their death. KH makes sure that acids do not create a sudden change with your aquarium pH by softening the water first before any pH change.

Fish naturally produces waste, ammonia, and nitrites. All of which are acidic and can affect your aquarium pH over time if you do not have a buffer. You must be mindful that this parameter does not reach zero because it could lead to troublesome instability.

Adjusting KH

The best way to decrease your KH is through reverse osmosis. RO system removes KH from your water. These allow you to have full control over the amount of KH you want to add to achieve your desired KH level for your aquarium.

If you want to increase this parameter, you can easily add baking soda/ soda ash (sodium carbonate or bicarbonate). An increase in the carbonate level means an increase in alkalinity. Just like in GH, you can also use crushed corals and rocks (example are dolomite rocks and aragonite) that naturally contain minerals that can raise the KH level. However, be mindful because these could also affect your aquarium tank GH and pH levels.

Third Parameter:

Importance of pH

pH is the measure of the acidity and alkalinity of water. It ranges from 1 to 14, 7 being the neutral pH, ( less than the neutral value are acidic) (more than the neutral value are basic/alkaline). You must be mindful of your water pH because a small point difference in pH is significant and could drastically affect your aquarium and could hurt your fish.

Fishes that have soft water as the natural habitat prefer acidic water and fishes that have hard water as the natural habitat prefers basic/alkaline water. Fishes that are not in the water with similar parameters as their natural habitats will have a hard time growing and breeding.

Adjusting pH

Again, like the other stated parameters, the best way to decrease or lower your pH is by using the RO system. Ro system produces a neutral to slightly acidic water. Lowering pH means making your water acidic(remember that pH lower than seven are considered acidic).

Increasing your pH means to make your water more basic or alkaline (remember that pH higher than seven are considered basic/alkaline). You can do this by adding calcium carbonate in your water. You can also add limestone, crushed corals, and aragonite to increase your water pH.


Setting up an aquarium to support marine life could be challenging. These involve careful research and planning. It is difficult to recreate an environment that is similar to the natural habitat or fishes and other marine living things.

Reverse Osmosis system provides aid to this problem because the water produced from this system is consistent. It allows you to have a clear idea of your water content and characteristic without the need for testing it in certified laboratories. With RO water, you can now adjust the three vital parameters(namely GH, KH, and pH) according to your aquarium needs.

As always, do not hesitate to ask for professional help when you ever get confused.