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Learn to Manage Water in Aquarium & Improve its Quality

Does your tank frequently run into problems with water chemistry?

Are uneaten food scraps affecting your tank population?

Are you looking for quick and effective strategies to manage water quality?

If so, you should know how to manage water in your aquarium.

Finding the right balance of water chemistry is like solving a complex puzzle. You don’t want to risk offsetting one variable too much, or you could throw off the entire balance in your aquarium.

For instance, if you plan on adding live plants into your tank, you will have to add fertilizer to provide them with the proper nutrients so they can grow.

However, if you add too much fertilizer, you could completely disrupt the water’s chemistry and kill your fish in mere hours.

Worse still is that you could kick start the growth of algal blooms that can wipe out entire stock over a slow time as they compete for oxygen and lower oxygen levels in the tank.

In the case of a freshwater tank, balancing osmotic pressure is as simple as keeping the tank clean and ensuring that the pH and mineral composition of the water is within acceptable ranges. By contrast, saltwater fish require a lot more attention to detail to prevent death.

Different fish species have their specific range of water quality aspects (for the temperature, oxygen concentrations, alkalinity, hardness, pH value, and more). They can survive, thrive, and even reproduce.

It is crucial only to adopt species that have overlapping tolerance limits. Bonus points if the fish share the same optimum range for water chemistry, this is the range at which they perform best. Refer to their care instructions for more details.

Your fish will show poor growth, and disruptive behavior, develop diseases and become vulnerable to parasitic infestations outside these optimum ranges.

If you allow the water conditions to deteriorate too much, your fish may end up dying.

In this guide, we will give you the complete step-by-step guide to managing water in your aquarium, the tools you need to evaluate the chemical composition of the tank, and easy methods you can use to restore balance to your tank should the conditions go outside of normality.

Managing Aquarium Water Chemistry

Water Hardness

Water hardness can be confusing, and many fish keepers don’t take the time to understand it, although they are just as important as the pH level in your tank. Many fish will not survive outside their tolerance levels for water hardness and will go through undue stress leading to their eventual demise.

We cannot stress how important it is to get suitable water hardness in your aquarium because you won’t be able to moderate the pH levels effectively.

So what is water hardness for fishkeepers?

Simply put, it is described as the number of mineral levels dissolved in the water. Hard water has a high amount of dissolved mineral content. A low amount of mineral content means that water is ‘softer.’ The most abundant mineral in water is calcium.

Our tap water, in most cases, is either slightly hard or soft, depending on its origins. Well, water from areas with high dissolved limestone is considered to be complicated. Water that comes from rainwater and lakes doesn’t have much mineral quantity, which makes it soft.

As a general rule of thumb, hard water has a high pH value. Soft water, by contrast, has a low pH value. It is because the minerals act as a buffer to prevent the acidification of the water.

The resulting water is, therefore, more alkaline and has a higher pH value. Some fish species prefer hard water, while others require soft water.

You cannot fix the pH value without first correcting the water hardness. For example, if you add a pH decrease into your tank with hard water, the mineral will make it difficult to lower the pH. Start by removing the mineral from the water before you can lower the pH.

It is done best with the help of a natural water softener. Another effective method is to use demineralized water for your fish tank.

The same applies if you’re trying to raise the pH value in acidic water that doesn’t have a high mineral quantity. Until you add more minerals to the water, you won’t be able to alter and maintain a high pH value. So what is your best course of action? You can add a calcium-based rock to increase minerals, thus making your soft water harder.

If you’re a beginner at fishkeeping, we recommend tailing your aquatic life around your existing water sources.

pH Value

There are many efficient ways to regulate your water’s pH value. You can use chemical additives that can directly raise or lower the pH value. Non-commercial natural agents can also alter the pH value. Adding peat to the aquarium and filter will increase acidity. Minerals are also effective at increasing alkalinity and pH.

It is worth noting that you will also cause undue stress to your aquatic life every time you change the pH value. Change the pH value slowly, never more than 0.3 pH in 24 hours. It should give your fish enough time to adapt to their new environment.

Ammonia, Nitrite, and Nitrate Management

Creating a nitrogen cycle is one of the most basic precursors to good tank maintenance.

Ammonia, nitrates, and nitrites are a side product of fish waste and are very toxic to your fish and plant life. Without proper checks and balances, it is effortless to accumulate fish and plant waste in the tank. The best solution is to allow ‘good’ bacterial colonies to grow in your tank so that they can break down nitrogenous waste.

Here’s how it works:

  • First, the waste from plants and fish is broken down and released as ammonia
  • Nitrifying bacteria convert the toxic ammonia to nitrite
  • Nitrite is also very toxic and is then converted into nitrate by ‘good’ nitrifying bacteria
  • Nitrates are not as harmful and can be used by algae and plants to grow

High levels of nitrites and ammonia are lethal for your fish.

You can do many things to effectively control the levels of nitrates in a tank without the need for external chemical interventions (that could disrupt the water quality).

Phosphate Management

Phosphates aren’t talked about very often, but they are crucial to the growth of algae. Elevated levels of phosphates can undoubtedly add to the difficulty in upkeep requirements since they’re used as nutrients by algae.

The leading cause of high phosphate levels is dry fish food, significantly lower quality foods that naturally contain phosphate.

Suppose your tank has a sudden outburst of algal growth – phosphate test. Use filtering materials to remove phosphate from your tank. You can add filtering materials to your filter media to remove phosphate from the water.

Aquarium Water Test Kit

You can keep track of all these distinct elements in your tank with the help of the best aquarium water test kit, readily available on Amazon and other online stores.

Our favorite is the API Freshwater Master Test Kit. It can examine your aquarium and tap water for nitrites, nitrates, ammonia, and pH value in one fell swoop.

More importantly, the kit is reasonably priced and can match any budget. It is easy to use for beginners and comes with detailed instructions on how you can manage it.

It can only be used in freshwater tanks but does not provide a high enough accuracy.

Use the API Saltwater Master Test Kit to gauge ammonia, nitrate, nitrite, and pH values.

Managing Other Factors

Feed them Less Frequently

Food can be good and evil. Good because it provides your aquatic life with the nutrients they need to survive and thrive. Bad because in excess quantities, your fish will ramp up production of bioload (waste products) that can easily disrupt the entire water chemistry in a matter of hours.

But by far, the worst offender for water chemistry is the presence of leftover food. Harmful organisms such as worms and toxic bacteria will eat the leftover food and increase the nitrate levels in the tank, kicking off a cycle in the tank that breeds bacteria and algae.

It is why it is essential to remove uneaten food from your tank as soon as you spot them.

Keep a small net handy to scoop out food scraps from the tank after you’re done feeding your fish. Speaking of feeding, you should provide your fish with small feedings two to three times every day (this may change depending on the species you’re looking after).

Get Rid of Worms

Buy a gravel vacuum and use it regularly. Gravel vacuums are handy when it comes to cleaning the tank and maintaining it in between water changes.

They’re incredibly effective at removing fish waste and food debris that sink to the bottom of the tank and get trapped in the debris. Most experts recommend using gravel vacuums and claim that they are highly efficient when used on the sides of the aquarium glass, plants, and below the substrate.

The best part about gravel vacuums is that they don’t require you to move your fish species out of the tank.

If that still doesn’t solve the problem, it’s time to use a more robust strategy.

Enter hydrogen peroxide.

Hydrogen peroxide is a little extreme, but you can use it to kill off those pesky detritus warms. Even though diluted hydrogen peroxide doesn’t harm aquatic plants, it can still kill your fish stock. So make sure to remove them before adding hydrogen peroxide (or something similar) to your tank.

Hydrogen peroxide effectively prevents algae from growing on plants and can also kill larvae, eggs, snails, and other species that share similar properties that could harm the tank and your animals.

Prepare a solution with 1 part hydrogen peroxide and four parts water. Dip your plants and wash your gavel in the solution before putting them back in the tank. It will take care of any pests, such as detritus worms. It is best to consult with a professional before attempting this method.

Use Filter

The tank’s filtration is usually at the root of all problems. The fish tank filter is supposed to cycle the water and minerals and keep the ecosystem in pristine conditions.

However, it is not uncommon for the filter itself to need regular cleaning. All that filtering does result in the accumulation of debris in your fish tank filter that needs cleaning.

If you don’t clean your fish tank filter, it will begin to lose its efficiency. Your aquarium’s water quality will start to deteriorate rapidly and become a breeding ground for parasites and worms.

One excellent option is to use mechanical fish tank filters. They’re high quality and require less maintenance. Mechanical filters are more adept at cleaning the water and ensuring that the tank remains clean.

Most fishkeepers agree that filtration is the most crucial component of a fish aquarium. It makes sense because if the water is not appropriately cycled, the fish will suffer, and plants will decay. Algae will start growing uncontrollably, and the substrate will be teeming with snails, worms, and other pests that you don’t want in your tank.

Change the Water Regularly

It is essential to change the aquarium water regularly, even if it looks clear. The truth is that if you were to stir the substrate up a little bit, you’d be shocked at the number of residues present.

It is not a problem in the wild because waste products from fish, animals, decaying matter, and uneaten food are naturally filtered. The harmful ammonia and nitrites are naturally removed before it gets to the point of extreme toxicity.

Moreover, the natural substrate at the bottom of the ocean acts like a powerful filter that absorbs harmful chemicals and decaying matter.

The sheer scale of rivers, lakes, and oceans keeps aquatic life healthy for a long time to come. As a general rule, the larger the body of water, the easier it is to purge waste. The only way to mimic this in an aquarium environment is to change the water regularly partially.

And yet, waste products are not the only reason the water has to be renewed. Trace minerals and chemicals in the water that contribute to the stability of the water and your fish are equally essential. Over time, these minerals are either used up or filtered out. If these minerals don’t get replaced the moment they’re cleared out, the pH value of the water will start to drop.

Moreover, the absence of water minerals will negatively affect the health of your fish and ‘good’ bacterial colonies that are responsible for removing the ammonia from the water. Giving your fresh fish water is like giving them minerals and vitamins to keep them strong and healthy.

What frequency of water change should be implemented?

The frequency of the water changes depends on the size of the tank and the number of fish you have. Smaller tanks with lots of fish will require more frequent changes than larger tanks with fewer inhabitants. Fish (and even plants) will generate tons of bioload that need to be recycled.

Experts say that it is best to change at least 15% of the water every week. Increase this number to 20% if your tank is heavily stocked. A tank with fewer fish can get by for two to four weeks without a water change, but you should not wait any longer to change the water.


Most fish keepers don’t know this, but there is a significant connection between your tank and water chemistry’s light levels. Aquatic plants need a planted tank for photosynthesis – fertilizers will only get you so far. Make sure to install light fixtures that are compatible with your aquatic plants.

It is worth noting that different plants have different requirements for light intensity, make sure you know the care requirements of the aquatic plants before putting them in your tank.

Can avoid this problem if you decide to choose plastic plants. However, if you decide to adopt live plants, it’s best to use a system of color coding to identify their lighting requirements.

Plants in the green category will live in low light conditions only, at around 0.2 to 0.3 watts per liter for growing bulbs and 12 to 25 lumens per liter for LED lamps.

Plants in the yellow category require medium light conditions only, at around 0.4 to 0.6 watts per liter for growing bulbs and 30 to 3 lumens per liter for LEDs.

Plants in the red category require high levels of light, which are at around 0.7 watts per liter for growing bulbs or 50 lumens per liter for LED lamps.

You can also use online calculators to aid you in the decision-making process for light fixtures installed in the tank. Here’s a good resource.