Both freshwater and saltwater aquariums require regular cleaning. Fish can’t survive in dirty water, that is why it is crucial to monitor the water quality. While cleaning fish tanks is pretty easy, most beginners just don’t know what to start with. Our detailed step-by-step instructions contain all the necessary information.

Table of Contents:

Cleaning Freshwater Aquariums
Cleaning Saltwater Aquariums

Cleaning Freshwater Aquariums

Before you start cleaning any aquarium, you need to make sure you have prepared proper tools for this. That is why we recommend to begin with compiling a list of supplies. Keep in mind that some of them need to be bought in specialized pet shops.

Check the List of Supplies

To clean one freshwater aquarium from A to Z you will the following:

  • Purified water (or special water conditioner that purifies tap water).
  • A tool for cleaning of inner walls of the tank from algae (a scraper or scourer).
  • A large bucket (a 5-gal one will do).
  • A mechanical vacuum for gravel (not a battery-powered one).
  • A cleaning solution for glass. Look for approved cleaners for aquariums or use a home-made solution of vinegar and purified water.

Optionally, you may prepare some extra tools and products, for example:

  • If you are going to change the filter, prepare new filtering media.
  • If you think your fish tank needs sanitary treatment, prepare a solution consisting of ¼ cups of bleach and 3 gallons of water.
  • A razor blade to scrub the dirt from the tank’s wall (for glass aquariums only).
  • Aquarium gloves.

Clean the Tank Walls from Algae

Use a clean algae pad or a scraper to purge the inner surface of the walls of algae and other types of bio contaminations. Gently scrub the walls to remove the organic dirt from the glass. If necessary, use a razor blade to get rid of stubborn patches. At this stage, you may want to wear aquarium gloves, which protect your hands and arms from water and dirt.

Never use your kitchen sponges for cleaning an aquarium! If you use a scrubber for cleaning a sink, it contains harmful detergents, which are toxic and extremely dangerous for fish. Buy a new sponge specially for an aquarium.

Calculate How Much Water You Want to Change

Approximately 25-50% of aquarium water per week needs to be replaced. The volume of the water depends on how fast the nutrients are accumulated in it (it is called the biological load). If you don’t want to replace water too often, you can choose to change a larger volume at a time (around 50%). On the other hand, more frequent water replacing helps to keep the content of nitrates and phosphates on a lower level.

Take the Old Water Out

Fish tank cleaning

Use a syphon to remove the old water from the fish tank to a bucket. Syphons are easy to use; moreover, they usually come with a manual. Some of them can be hooked on a sink, which adds convenience.

Vacuum the Gravel

Vacuuming is needed to clean the aquarium bottom from waste, food remains, and other kinds of organic debris. Make sure you are pushing the vacuum through the gravel deep enough to collect small fractions of debris from the very bottom.

  • Keep in mind that small aquariums habitats can be injured by the vacuum. To prevent this wrap its end in a net.
  • It’s recommended to clean about 30% of the gravel every month.

Aquariums with a sand substrate can also be vacuumed. To prevent sucking in the sand, keep the end of the vacuum at least one inch away from the substrate. Also, you can regulate the flow by closing the hole on the syphon end with a finger.

Clean the Aquarium Decorations

Over time, all the aquarium decorations get covered with algae and organic waste. That is why they require regular cleaning as well. If you do it on a regular basis, the algae is easy to remove with a sponge or a special algae pad. To remove stubborn stains you can use a new clean toothbrush.

  • If you fail to remove the dirt with a sponge, take the decoration out of the tank and put it in the bucket with a cleaning solution consisting of water and ¼ cup of bleach. After that, wipe off the algae with a sponge and rinse the item thoroughly in clean water (or tap water mixed with chlorine remover). Let the item dry in a natural way and place it back into the aquarium.
  • To reduce algae formation and accumulation try to decrease the exposure to light by moving the tank away from the window or using curtains.
  • Some live aquarium habitats can stop algae growth. They are, for example, an otocinclus, a flying fox or a rubbernose pleco.

Fill the Tank with Clean Water

Now, it’s time to add some fresh water. Measure the temperature of the prepared purified water with an infrared thermometer and make sure it is similar to the temperature of the water in your aquarium. Keep in one that the difference in 1-2 degrees can be critical for fish. Try not to overfill the tank when adding the water, or your fish can be accidentally spilled over together with extra water.

If you use purified tap water, you need to prepare it in advance. Add a recommended dose of water conditioner to the bucket with tap water one day before cleaning the aquarium.

Monitor the Transparency of Water

Just after the tank refilling, the water can seem cloudy. Usually, there is nothing to worry about. It takes several hours for the water to become clear and transparent. If it remains cloudy longer, there is a problem with its quality or the quality of the substrate. You may buy a special cleaning agent, but in most cases, they are useless, as they just mask the problem, instead of neutralizing the real cause of the cloudiness.

Wipe the Exterior

The outer surface of the tank is also to be cleaned. Use a clean wet cloth or sponge to clean fish tank glass. For the aquariums with glass walls, a usual glass spray cleaner can be used. That said, it is unsuitable for acrylic and ceramic tanks.

Cleaning Saltwater Aquariums

Cleaning a saltwater aquarium

The only important difference of saltwater aquariums from their freshwater analogs is water. To clean a fish tank of this type you will need some additional tools. Also, you’ll have to prepare the water itself in advance. Here is a step-by-step instruction on how to clean a fish tank with salt water.

Prepare the Water

The water should be prepared at least a day before cleaning the aquarium. Use purified (distilled or reverse osmosis) water only. Pour the water in a clean bucket and warm it up with the help of a special heater. After that, add some salt mix (both salt mix and a heater are available at pet shops). Follow the instruction supplied to find the right sale/water ratio: usually, it is around 0.5 cup of salt mix per gallon of water.

On the next day, test the salinity. For this purpose, you can use a special salinity probe, a hygrometer or a refractometer. Depending on the species inhabiting the tank, you may need a salinity of 30 or 35 grams per liter.

Finally, measure the water temperature. Most saltwater fish require a temperature of 73 through 82 degrees F.

Check the List of Supplies

The list of basic supplies for cleaning saltwater tanks includes the same items as those required for freshwater aquariums. These are an algae pad, a separate 5-gal bucket, a gravel vacuum, and a glass cleaner. Additionally, you will need pH strips, a salinity probe (or a hygrometer/refractometer), and a thermometer. Optionally, you may want to use bleach and replace filtering media.

Remove the Algae

Use an algae pad or sponge to clean the inner surface of the tank’s walls from algae and organic residues. Additionally, you may use a razor blade to remove stubborn stains.

Take Out 10% of Water

For saltwater tanks, it is recommended to change approximately 10% of the water twice a month. By doing so, you reduce the level of nitrates and improve water quality. Removing extra water is pretty simple: all you need is a usual syphon.

Vacuum the Substrate

Vacuuming of a saltwater aquarium is similar to the vacuuming of a freshwater tank. Use a syphon-type vacuum cleaner to gather the organic waste from the tank’s bottom and clean fish tank gravel. If you have a gravel substrate, push the end of the vacuum through it to reach the bottom. If you have a sand substrate, keep the vacuum end at a distance of 1 inch away from it and mix the sand with your finger. The owners of very small aquarium habitats may use a fish net wrapped around the vacuum end.

Clean the Aquarium Decorations

If the decorations are moderately contaminated, you may clean them without taking out of the tank. Just wipe them with a pad or scrub with a new toothbrush to remove the algae. If you need to clean fish tank rocks that are very dirty, you need to take them out and put in a bucket or a container with a 10% bleach solution. After that, rinse them in pure water (distilled or purified with water conditioner), let them dry, and place back to the tank.

Remove Salt Creep

Salt creep is a hard salt residue, which is formed on the aquarium walls when marine water evaporates. You can remove it with a pad or a sponge. After that, you can put it back into the water and mix it.

Fill the Tank with Water

Now, it’s time to add some water. If you have taken out 10% of the old water, you need to add exactly the same amount of new water. Make sure the temperature and salinity meet the requirements. Pour the water into the tank but try not to overfill it.

Monitor the Temperature

Use a high-quality aquarium thermometer to measure the temperature of the water every day. Most saltwater fish are pretty delicate. They can’t survive if the water temperature is slightly lower or higher than they need.

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Dean Banks

There are a few different contributing factors that will help in your deciding when the tank does need cleaned. 1.The size of the tank can often be one thing to take into consideration when you are going to plan how frequently the aquarium needs to be cleaned. From past observations we believe that smaller tanks seem to get dirtier quicker than larger tanks. 2.Another factor is the filtering system the tank has to keep the water fresh. The main purpose of this is to remove any excess food, fish’s waste and dangerous chemicals. 3.The type of fish and the quantity… Read more »

Alberto Howard


Justin Meyer

Is There A Fish Tank You Don’t Have To Clean?

Zack James

It is important monthly to keep an eye on the levels of ammonia, nitrate and pH levels within your tank and testing them once a month should be sufficient. Ideally they should be pretty steady from month to month, so keep a record somewhere safe so you have something to compare your readings to. Some indications of problems with the condition of your water can include cloudiness, a change in color, or if your fish are behaving abnormally. You should also clean your filter cartridges once a month.

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