How to Maintain a Freshwater Aquarium

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How to maintain a freshwater aquarium

Having doubts on how to maintain a freshwater aquarium? It is something more normal than we imagine. Even long-time aquarists only realize they are doing it wrong after so many of their animals die “inexplicably”.

Carrying out maintenance in the aquarium is easy, just perform the basic weekly maintenance: change the water, clean the tank and carry out the tests in the water. It’s a quick and easy thing that will prevent any kind of future problems and even fish disease.

When teaching new aquarists, the part I think is most important to talk about is tank maintenance. It is important to emphasize that maintenance is an essential part of the proper functioning and stability of the tank.

In this article, I cover all the factors on how to properly maintain freshwater aquariums, along with some tips I’ve acquired in decades working with aquarists.

General Tips on How to Maintain a Freshwater Aquarium

Aquariums are closed artificial systems. These systems depend on us, tutors so that everything remains stable and running smoothly. Our tanks are constantly going through different cycles and biochemical reactions, these movements generate (or terminate) various free compounds in the water.

One of the biggest examples is nitrate, which is generated from the breakdown of ammonia (which starts with free organic matter) into nitrite. This nitrite is then consumed by the beneficial bacteria of the aquarium, being transformed into nitrate. We must remember that in nature nothing is lost, everything is transformed.

The nitrate generated is then in our aquariums, being removed only in 2 ways, either via plant absorption (which in the aquarium environment is not a viable alternative) or via partial water exchange.

As with nitrate, there are a variety of compounds that must be actively removed via water exchange.

Another important point is cleaning the tank, with techniques such as siphoning the substrate and removing leftover feces, debris, and food. We perform these tasks so that the aquarium maintains a low bioload. Thus keeping the water of good quality for longer.

Cleaning equipment such as filters and changing the media that compose it is vital. This is an area where a lot of dirt deposits occur, so you should remove them.

Water change is probably the main aspect of good maintenance, but without dirt removal, you’ll be in a constant battle with pH drops and nitrogen spikes.

Water exchange is also important for mineral replacement. Water contains minerals dissolved in it (such as calcium, magnesium, etc.), these minerals are absorbed and used by the plants and animals that make up your tank. The best way to replace these minerals is through a water change.

Periodic Maintenance Work Schedule

You must perform its maintenance periodically. There are two ways you can schedule your maintenance. One of them works to prevent future problems, and the other just corrects parameters that are destabilizing.

Weekly maintenance is what I always recommend to my students and also to the various stores I provide services. Carrying out basic maintenance every week we prevent any kind of problems and instabilities. Another important point is that with frequent maintenance, the fish get used to it and in a short time they will no longer be stressed, even feeding after an extensive water change.

During 7 days, its parameters will hardly destabilize or suffer some kind of peak, either from ammonia or algae. Likewise, in rare cases, the tank will have a high organic load of debris, with the filters always working without clogging and the bacteria within their stability. Algae will also not have enough nutrients dispersed to proliferate and become a problem.

In this type of maintenance, we prevent problems, because we take action before something happens. It’s the safest way to go, especially in tanks up to 80 gallons. Because the tank’s conditions are always optimal, it is performed quickly and without much effort.

In these cases, heavy cleaning (which includes cleaning the filters, decorations, etc.) is much more sparse and can be carried out monthly.

The second type of maintenance is the one I see the most around. In practical terms, this technique is not even maintenance, being considered a type of correction. This maintenance consists of measuring the parameters of the tank’s water, and when they are out of standard, then we carry out the maintenance.

The parameters taken as a basis for carrying out the cleaning here are several. Tests can be done in the water, or just a holistic observation, looking for color change in the water, fish with closed fins, foam in the water, or spots of algae.

In practical terms, we wait for the system to destabilize so we can restore it via maintenance. This type of approach is dangerous, and leaving the system overloaded for a while, can cause serious problems for its inhabitants.

When we notice visual changes or changes in the test results, it means that our aquarium has been destabilized for some time and is now approaching the critical point. In these cases, the period between maintenance is usually 3 to 6 weeks and there is a high accumulation of debris and compounds in the water. Aquarists who use this technique also make mistakes because their maintenance is based on some immutable procedures, such as changing only 30% of the water.

It is very common to hear reports that the person always loses fish after these spaced maintenances. Among the various reasons, I will cite as an example a negative factor of sticking to procedures considered outdated.

We have had an aquarium for 6 weeks without maintenance, and ammonia is already forming in the tank. In addition, the pH dropped due to the accumulation of organic matter.

When performing an exchange of only 30% of water, this volume will not be enough to remove all the dispersed ammonia, but it can raise the pH to ideal levels. With the higher pH, the ammonia will become toxic, and will likely kill some fish.

This 30% probably won’t even be enough to remove all the dirt accumulated on the bottom and the substrate.

Another important point to note is that in these cases, you have a lot of work, carrying out heavy maintenance, cleaning filters, removing algae from the glass and decorations, etc.

If you choose to use this route, be aware that this instability of parameters is extremely harmful to the fish in the system itself. And it is vital to always carry out tests after performing maintenance, only then will you ensure that everything has been fixed.

How To Clean the Water

Proceeding with the correct maintenance is simple, and should be effortless. If cleaning your tank is taking a lot of work and time, review your system and the way you clean your water.

The first step to performing maintenance effectively is to have all items for the exclusive use of the aquarium on hand. Things like

  • Siphon;
  • hoses;
  • cleaners;
  • sponges;
  • buckets;
  • dry cloths;
  • fishnet;
  • tweezers;
  • Products (acidifiers, water conditioners, etc.);
  • And everything else you use.

Such equipment is essential for good and safe maintenance practices, and should always be clean and on hand. With everything within reach and easy to use, the water change becomes more efficient. Remember that water change will always be a stressful procedure for aquarium inhabitants, the shorter the time we do it, the better.

With everything within reach, let’s begin maintenance.

We must disconnect all equipment from the power source. This is an essential step to make the process safer, as it avoids shocks and equipment malfunctions.

If we are carrying out basic maintenance (only on the aquarium display), we should start by passing a soft sponge (or equipment for this purpose) all over the inside of the aquarium’s glass. In this procedure, algae and other dirt embedded in the glass will be removed, leaving everything in suspension in the water column.

The next step is with the help of the net, to remove large debris such as leaves and dead plants, and food remains. This step is not essential, but it ensures that maintenance equipment (such as hoses and siphons) is not clogged with large debris.

After carrying out the removal of larger dirt, we took the siphon and began to remove the water. While we remove the water to a bucket or straight to the drain, move the submerged tip of the siphon through the aquarium, removing the dirt and also putting it in the substrate. This step is essential to remove dirt from between the substrate and in hard-to-reach places.

Carry out this procedure until we have removed the desired amount of water. The idea is to remove the minimum of 50%.

The next step is to fill the aquarium with new water. For this we must first measure the parameters of the tap water and, if necessary, make the corrections; so we avoid physiological shocks in the fish and other problems. The idea is that the correction is made in a bucket or other container that is not the aquarium.

With the help of the bucket or hose, we will fill our aquarium to the required water level. Remember to use a water conditioner to remove unwanted substances like chlorine and chloramine.

After filling the tank, reconnect the equipment and check if everything is working normally. And that’s it, we’re done with our weekly basic maintenance.

Deep maintenance should be performed monthly or every two weeks. You must perform it along with basic maintenance.

Remove your filtration system and open it. You should change chemical media (such as activated carbon), and clean biological (such as ceramics) and physical (sponges) media. To perform the cleaning of the media, simply rinse it with water taken from the aquarium.

You should always use aquarium water for these cleanings, otherwise, you can kill the beneficial bacteria that live there.

Decorations should also be cleaned at this stage. Preferably also use aquarium water, but depending on the state, you can wash them directly under the tap with the help of a cleaning sponge and without the use of chemical products.

The filter housing can also be washed directly over the faucet. Remember to disassemble the bomb parts and also clean them. Dirt may accumulate near the impeller.

After carrying out this deep cleaning, fill the aquarium in the aforementioned way and turn on the pieces of equipment.

How To Test the Water and What Parameters Need To Be Tested

One of the vital tasks of every aquarist is performing water tests. Testing the aquarium water is the only way to know the condition of our tank.

These tests can be purchased at aquarium stores and are easy to perform. Just follow the manufacturer’s information, but basically, they all work the same way. Put some of the water to be tested in a container, add the reagent and wait for the color to change. When the color changes, compare it to the color in the table.

Most tests work by demonstrating a color, which will be compared in a table with the data to be read. Each species needs an ideal parameter of factors such as temperature, pH, and hardness. Through the tests, we will check if the aquarium is suitable for a certain fish.

Always try to get quality tests, the better the test, the more accurate it is. Always test your water before and after performing the water change. Testing tap water is also important, only then will we know which parameters need to be corrected.

pH Level

The pH index is one of the most important factors to keep stability in the aquarium. Each species occurs at a specific pH, which can be neutral (7), basic or alkaline (above 7), and acidic (below 7).

Regularly test the pH to see if it is within the desired range and is stable. Fluctuations in pH bring numerous damage to fish.

Ammonia Levels

Ammonia is the terror of aquarists, it is a toxic compound for fish that is naturally generated in the aquarium. In addition to being generated through the breakdown of organic matter in the tank (such as feces and food scraps), fish also excrete it directly through their breath, feces, and urine.

Ammonia is the main food for aquarium bacteria and should always be at 0 in tests. High ammonia levels indicate polluted water. This polluted water can occur due to insufficient filtration, overpopulation in the aquarium, and overfeeding of fish, among other factors.

Nitrite Levels

Nitrite is the first compound to be generated when bacteria degrade ammonia. It is less toxic than ammonia, but it can still cause poisoning problems.

This compound must always be at 0.

Nitrate Levels

The nitrite is then converted (also by nitrifying bacteria) to nitrate. Nitrate is less toxic than nitrite, but it must also be removed from the aquarium. Its index must always be at 0.

There are only three ways to get it out of your tank water. With the use of specific resins, water exchange, or assimilation by plants.

Plants use nitrate as food, but in a conventional aquarium system, we will hardly have sufficient amounts of plants to efficiently lower this compound. Resins are a good choice, but they are expensive and must be constantly renewed, which does not make them very efficient.

Changing the water is the best way to get rid of nitrate. Among many reasons, a high nitrate means that probably ammonia and nitrite are also at unwanted levels. The water change combined with maintenance is the best way to readjust the water quality.

Phosphate Levels

Phosphate is not one of the most talked about nutrients in freshwater aquariums, only among those who work with planted tanks. For saltwater aquariums, it is a compound that must be controlled for the good development of corals.

Phosphate is one of the compounds generated by the breakdown of organic matter and is not consumed by bacteria, only by plants, which, once again, are not an efficient form of filtration.

In planted aquariums, 0.5 to 1 ppm is a good amount. In aquariums with fish, keep as close to 0 as possible.

Water Hardness Level

In aquariums, water hardness is a quantity closely linked to pH, and concerns both soft and hard waters. Soft water is generally acidic and has low levels of mineral salts diluted in it. Hard water is water with a high content of these minerals.

It is an important factor, especially in the reproduction of some fish, and must be controlled.

The ideal level depends on the species to be kept. As an example, rift valley cichlids inhabit hard water with high amounts of salt. South American cichlids inhabit soft water.

Risk of Contaminants

When using tap water, we run the risk of putting unwanted compounds in our aquarium. That’s why carrying out several tests before putting it in the aquarium is so necessary.

The water from the supply network is treated with some chemicals, these chemicals are vital to make it drinkable for us humans, but many of these compounds are toxic to fish.

The main ones are chlorine and chloramine, the latter being the worst. Chlorine is not very toxic, in addition, it quickly volatilizes into the environment, leaving the water. Chloramine is highly toxic to fish and is non-volatile.

Tap water can also contain other elements such as fluor and even heavy metals.

The product called water conditioner is responsible for treating tap water, leaving it ready to be populated by fish. When changing the water, always use a good quality conditioner.

Impact of Food in The Water

Feeding our fish impacts water quality in different ways, so we must always use high-quality feed and feed our fish in the correct proportion.

Low-quality commercial fish food, the moment they touch the water, they start to lose and release nutrients, these nutrients will be free in the water, polluting it little by little. Better quality feeds are made up of ingredients that resist contact with water longer, delivering everything to the fish, and polluting the water little.

Offering the correct amount is necessary for two main reasons. The first is for the fish to eat the correct amount, avoiding obesity.

When overfed, fish, in addition to suffering from the accumulation of fat in the organs, release a large number of feces and urine, that is, they directly release a greater amount of ammonia into the water.

When we offer a large amount of food, a part of it will not be eaten by the fish, being accumulated in the water. This accumulation is nothing more than organic material that will decompose and degrade the quality of water.

Fish That Contaminate the Aquarium More Than Others

Some fish are known to emit a large amount of bioload into the water. This is either because their metabolism is very fast. Or because they feed and defecate constantly in the aquarium.

These species are known as messy fish, and among the main ones we can mention are plecos, carps, and goldfish.

When keeping these animals, it is important that you carry out periodic maintenance and that your aquarium has a properly sized and functional filtration system.

Top 10 Maintenance Tips

Now we’ve seen all the basics involving aquarium maintenance and parameter testing. I will now provide you with some valuable tips so you don’t have a problem with maintenance

1. Turn Off The Equipment

When performing the water change, remember to always turn off the equipment. Most items used in aquariums have to work underwater. If we remove the water with the equipment on, these pieces of equipment will break.

2. Equalize The Parameters

Always equalize the parameters of the water to be placed in the aquarium. Leaving the new water with the temperature, pH, hardness, and everything else in the conditions already established by you is the best way to avoid problems in the fish after a water change.

3. Use The Correct Equipment

Changing water and cleaning can be done with just your hand and a bucket, but that doesn’t mean it’s the best way. Getting items like siphons, hoses, cleaners, etc., will help you do less work and increase your cleaning efficiency.

4. Exclusive Use In The Aquarium

Items used for maintenance must be for the exclusive use of the aquarium, without contact with contaminants such as chemicals or other types of liquids.

5. Use a Water Conditioner

Always use a water conditioner, otherwise, you can poison your fish.

6. Test Tap Water

Always test tap water, so you can check if you need to modify any parameters such as pH before putting it in the aquarium.

7. Test The Water After Partial Change

Sometimes, especially when we have ammonia spikes, a water change below 70% will not remove all the toxic compounds. Always test your aquarium after performing the water change, that way you can check if everything is ok.

8. Perform Maintenance Regularly

The more you clean your tank the better, establish a strict routine, preferably weekly, to clean your tank. That way it will always be stable and clean.

9. The More The Better

Despite saying that you can never change too much water, this is a lie. The greater the amount of water removed from the aquarium, the greater the renewal and the better for the fish.

10. Get Quality Products

Saving on fish food, water conditioners, water-correcting products, and even equipment can be costly in the long run. Cheap products deliver what you pay for, and are unlikely to be highly efficient in keeping your aquarium stable.


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