How to Properly Clean a Fish Tank

Why Clean Your Aquarium?

Just like anything else inside your home, aquariums get dirty. If not cleaned regularly, your aquarium may have an excessive bio load and toxic water. Obviously this will create a harmful situation for your fish and plants. 

While the filter inside the tank does help clean the water, there is a lot more that needs to be done to keep the water conditions stable. There can be a lot of debris like uneaten food, decaying plant matter and other waste that accumulate over time in your aquarium. Almost everything inside the tank needs to be cleaned regularly. Even the filter media needs to be cleaned and replaced to maintain the balance of organic compounds inside the tank. 

One more reason to clean your aquarium is to prevent algae build up. Algae can make the water look dirty or cloudy and can accumulate on the walls of your aquarium. The algae can create a haze in the water and make it difficult to see things in your aquarium. 

The Equipment Needed to Clean Your Aquarium

  • Algae Scraper/Pad
  • Razor Blade
  • Gravel Vacuum Cleaner
  • Sponge
  • Bucket
  • Scissors (for trimming plants)
  • Net (to remove floating debris)
  • Water Conditioner (Dechlorinator)
  • Toothbrush (optional)
  • Replacement Filter Media
  • Bath Towels/Cloth
  • Vinegar/Aquarium Glass Cleaner

How to Clean Your Aquarium

If you are cleaning your fish tank for the first time then you should take your time and go slow to make sure nothing is missed. You don’t want to do something that will unnecessarily stress or harm your fish. 

Many tutorials talk about removing all the water from your aquarium by placing the fish inside small containers or bowls. We don’t recommend removing all the water because it may stress your fish. You should only do this if the fish tank is extremely dirty and cleaning it is impossible without emptying everything. For most fish tanks, removing only a part of the water (up to a maximum of 75%) will be enough to completely clean your aquarium. 

Step 1: Turn off the Filter

The first thing that you should do is turn off the water filter and heating equipment inside your tank. If you have a CO2 diffuser or any other equipment, turn them off as well. These types of equipment are not supposed to function without water and can get damaged if kept running while you are cleaning your aquarium.

The lights can be kept on because they won’t be impacted by the cleaning process. The air pump should also be kept on. If the water temperature drops a little during the cleaning your fish should be fine. In the wild the temperature typically fluxuates by up to 10 degrees for several hours. This little bit shouldn’t be a problem for them.

Step 2: Removing Algae

The next step to cleaning your fish tank is removing algae from the inside of the aquarium walls. Sponge or algae scrapers are great at removing the algae. There are many types of algae scraper available in the market like plastic, glass and magnetic algae scrapers. 

Magnetic scrapers are great as they don’t require you to get your hands wet to clean the algae. One part of the magnetic scraper needs to be placed inside your aquarium and the other on the outside. Both will be held together on the glass using a magnet. Moving the outside end will move the inside end as well. As you move the outside across the outside walls of your aquarium the inside scraper is scrubbing the algae off.

If you have an acrylic fish tank, use a scraper that won’t scratch the acrylic. Make sure you get an algae scraper from a pet store and not from a local hardware store. Both may look the same but the algae scraper bought at a hardware store might be more abrasive and leave scratches in your aquarium.

Take the algae scraper and gently scrub the front glass wall of your tank. Bring it across the entire glass surface to ensure all the algae is removed. If the glass walls have a lot of algae, you might have to use a razor blade to remove it. Try not to disturb the substrate while cleaning the inside walls. 

Cleaning the front and side walls shouldn’t take much time but the back wall can sometimes be difficult. If you have background plants in your aquarium, try not to move them around more than you need to while removing the algae. 

Step 3: Cleaning Decorations

Once the inside tank walls are cleaned you can move onto what might be the hardest part. Artificial plants, rocks and decorations can be the most difficult because they can be hard to clean well. Using a brush or a sponge can help you get into the small spaces to better clean them. If they are very dirty, they should be taken out of the fish tank to be fully cleaned. Place them inside a tub or bucket. Make sure not to use soap or detergent to clean them. Any residual traces of soap can be harmful to your fish.

Soak the decorations or artificial plants in lukewarm water and use an algae scraper to clean them. If they are very dirty, soak them inside a 10 percent bleach solution for around 20 minutes. The bleach will help get rid of the excessive algae and debris. You can use a toothbrush to remove any residual debris and rinse them under tap water.

Depending on the size of your aquarium you may have a number of decorations and it might just be faster to take them all out. One popular short cut is to put them in the dishwasher without soap. The dishwasher lets hot water spray all over the decorations and get the majority of the gunk off without you needing to scrub anything.

Let the decorations and artificial plants dry completely. This will remove any traces of bleach. They should not be placed right away inside the tank because there is a lot more to clean. To remove any traces of chlorine you should dip them in a bucket of water and add a small amount of water conditioner.

Step 4: Cleaning and Trimming the Plants

If you have living plants inside your aquarium then they will also need to be cleaned to make everything look vibrant and natural. Cleaning living plants is also important because they are a natural filtration source for your fish tank. Some plants may have dead parts and need to be removed so that they don’t release toxic chemicals that can hurt your fish.

Trim the leaves and branches of the plants if they are too big and obstruct the growth of other aquatic species or prevent light from reaching the bottom of your aquarium. Use a pair of long scissors to trim the plants. Remove any dead plants from the tank. Gently pull them up near their base to uproot them. Be careful so that the surrounding plants don’t also get uprooted. If they do happen to come up also, do your best to place their roots back in the substrate.

If there is any debris on the plants, use a sponge to gently remove it. Using a sponge will also help remove any algae that may have grown on the plants. Some tanks may have floating plants that may have overgrown. If they create too much shade, they can either be trimmed or parts of them removed from your tank. 

After you are done trimming the living plants and removing the dead parts, use a net to remove all of the floating debris from your aquarium.

Step 5: Vacuum the Substrate

Next on the list is cleaning the substrate. This is the place where the largest amount of waste will have accumulated. You can use a gravel vacuum cleaner to clean the substrate. Before you start removing the water, make sure to turn off your air pump. The water level will drop while vacuuming the substrate and turning them off will keep the air pump from burning out.

If you want to read on how to vacuum your aquarium like a pro we have a full article here! 

Step 6: Removing the Water

After the substrate has been cleaned, use the gravel tube to siphon the water out to perform a water change. The amount of water that needs to change will depend upon the amount of fish you have, the bio load and the size of your aquarium. Tanks that are very dirty will need more water changed out. For most aquariums changing 25 – 30 percent is all that is needed when doing a monthly cleaning. 

If you have not cleaned your aquarium for a long time and it has become very dirty, it can be tempting to change out 50%. This is a bad idea because it can actually hurt your fish. 35% of the water is already a lot, and this much water should only be removed during a serious cleaning. If your aquarium is extremely dirty, wait a few days and then do another 20-30% change. The few day delay gives your fish time to adjust to the new water and wont be such a shock for them.

Keep a close watch on the bucket catching the dirty water so that the water doesn’t overflow on the floor. If your bucket is almost full, stop the siphon and empty the bucket. You can pour the water down the drain or use it to water the plants in your garden. If you have a garden we highly recommend you pour it in there. All the fish waste is great for growing plants! Then restart the siphon to remove the remaining water if needed.

Step 7: Refilling the Water

Freshwater Aquariums

The amount of water that you removed needs to be added back into your aquarium. There are two important things that need to be looked at while adding water from your sink. The chlorine level and temperature of the water.

The water that is going to be added to your fish tank should be the same temperature as what’s already inside. You can adjust the faucet to match the warmth of the water with the water inside the tank. If you have a hose long enough you can run it directly into your aquarium. Most people prefer to fill pitchers of water. This lets them dechlorinate the water before it’s added in, and lets them double check the water temperature. 

If you decide to use a hose, the flow of the water should be moderate but not too fast. This helps quickly raise the water level and the refilled water absorbs the dissolved nutrients. You will want to add a dechlorinating solution into your aquarium if your water is chlorinated. This will neutralize the chlorine and keep your fish from getting stressed or hurt.

There are many brands of dechlorinator available. Follow the instructions given on the label to see how much of the dechlorinator should be added.  Dechlorinators work instantly to remove the chlorine, and it’s safe to add it into your aquarium. It doesn’t hurt to very gently mix it into the water either. Just be careful not to create a current that will frighten your fish too much.

Saltwater Aquariums

Performing water changes for saltwater aquariums is a little more complex than freshwater aquariums. Along with the temperature and chlorine levels the salinity level of the water also needs to be checked. It is done by adding salt to the water that will be added inside the tank.

The water should be prepared a night before performing the water change. Reverse Osmosis (RO) or Deionized (DI) water needs to be used. You can purchase this from your local grocery store. Depending upon the amount of water that needs to be added, take a bucket that’s large enough and add the RO/DI water.

First dechlorinate the water by following the instructions on your dechlorinator bottle. Next, heat the water to match the temperature of your aquarium. A specialized heater can be purchased to heat this water. Add the required amount of salt mix to the water by following the instructions on the label. The salt mix needs to be added while the water is moving. It’s best to stir the water while you are adding the salt in. If you have an extra air pump you can let the air agitate the water as well.

Let the water sit overnight. It will help the salt mix to dissolve completely in the water. Measure the water conditions with an aquarium water testing kit. The salinity and temperature of the bucket water should match with the water inside your fish tank. If everything looks good you can add the fresh water into your aquarium.

Step 8: Cleaning the Outside of Your Aquarium

The next step is to clean the outside of your tank. To clean the glass, it’s recommended to use a vinegar / water mix or an aquarium glass cleaner. Other types of glass cleaners contain ammonia that can be harmful for the fish inside your aquarium. You can use cleaners with ammonia as long as you spray the cleaning cloth away from your aquarium. Spraying the cleaning cloth will keep the ammonia from contaminating your water. Use a cloth or paper towel to wipe the glass. Then you won’t have any more smudges or fingerprints on your aquarium. 

Don’t forget to remove the lid and light from your aquarium and clean them with a cloth. These usually have a good amount of dust build up so it’s best to do this away from your aquarium.

Step 9: Putting Everything Back Together

Even after all the cleaning, your aquarium may still not look clean. One possible reason is there is a lot of particulate matter clouding the water inside your tank. This is completely normal and clears up after a few hours. Plug in the filter, heater and CO2 diffuser and turn them on. Wait for a couple of hours and the water should clear up.

The artificial plants, rocks and other plant decorations also need to be placed inside the tank. Take them out from the dechlorinated water and place them back inside your clean aquarium.

What many people will do is wait a day or two after they’ve cleaned their aquarium and they’ll vacuum again. A lot of the floating particles will be caught up in the filter, but many will still settle into the substrate. Using the gravel vac right after it’s cleaned will help keep the new fresh water cleaner longer.

Step 10: Cleaning the Filter

We recommend that you wait a week to clean the filter after cleaning the aquarium. This is because cleaning the fish tank will have disturbed most of the beneficial bacteria that was present inside. Filter media also contains a lot of beneficial bacteria that help break down toxic organic compounds inside the water. 

Cleaning all of them together can cause an ammonia spike. To minimize any ammonia spikes, it would be best to clean the filter a week or two after a full cleaning. This way a lot of beneficial bacteria will have grown back inside your aquarium.

How you clean the filter will depend upon the type of filter you have. Sponge filters are easier to clean than complex canister filters. You need to remove the sponge and scrub it with your hands. This will remove the debris from the sponge pores. If the sponge filter has any filter media, then that also needs to be cleaned or replaced.

For canister filters, the entire canister will have to be dismantled to take out the filter media. If the filter media has been damaged or worn out, they will need to be replaced.

Soap or detergent should not be used to clean the filter. Only tank water should be used to clean the filter box and the filter media. This will ensure it retains some or most of the beneficial bacteria.

Clean Your Aquarium Regularly

Regular cleaning is important for your aquarium. If you removed a lot of algae and debris from your fish tank, it could be because the tank has not been cleaned for a long time, or it could be a sign of a problem. To keep the tank conditions healthy and keep cleaning from becoming a difficult process, we recommend regular aquarium cleanings. 

For most aquariums, cleaning it once a month will be enough. Regular cleanings go a long way towards keeping your fish healthy and happy. The cleaner you can keep the aquarium, the less illness you’ll have with your fish.

It’s also a good practice to clean the tank immediately if you see any signs of an algae bloom inside your aquarium. Cleaning your aquarium then will keep the water from looking cloudy and create an imbalance of organic compounds inside the tank. The filter should also be checked and cleaned regularly, at least once a month. If the filter stays clean, the water composition in your tank should stay good.