Cleaning a freshwater aquarium is important for the health of the fish and keeping the aquarium attractive. Aquariums add beauty and life to a room but require dedicated care for the fish and diligent maintenance to preserve the equipment.

Sticking to a regular care schedule is ideal for a healthy freshwater aquarium environment and appearance. Algae scrapers, vacuums, thermometers, nets and gloves are the basic tools to clean an aquarium.

Freshwater Aquarium Cleaning Steps


  1. Assemble all your cleaning supplies and prepare your workspace.
  • Properly treated water in the replacement quantity
  • An algae pad for cleaning the glass inside the tank
  • A large bucket (typically 5 gallons) dedicated to aquarium cleaning
  • A simple siphon-type gravel vacuum. (Avoid a battery-operated gadget.)
  • Filtration media: cartridges, sponges, carbon packets, etc.
  • An aquarium-safe solution for cleaning the glass
  • A 10% bleach solution in a separate container (if needed)
  • Metal or plastic razor blade (if needed). Note that acrylic tanks are easily scratched.
  1. Clean the inside of the aquarium with the algae pad.
  • Run the pad along the sides, scrubbing as necessary, to remove algae that are sticking to the aquarium.
  • If you come across a difficult patch of algae, use a razor or plastic blade to remove it.
  • Do not use a household sponge, especially a used one, because it contains chemicals that are toxic to the aquarium. A clean, tank-only algae pad will prevent chemicals and detergents from entering the tank.
  1. Decide how much water you are going to change.
  • If you keep a weekly water-changing schedule and if your fish are healthy, remove 10% to 20% of the water.
  • If you change your water every other week, remove 25% of the water.
  • If you have a sick fish, remove a greater amount of water – at least 25% to 50%.
  1. Siphon out water from the aquarium.
  • Buy a new bucket and dedicate it to cleaning your aquarium. If you repurpose a household bucket, residue from other chemicals can be harmful to your fish.
  • Start the siphon and direct the old water into your bucket. Aquarium siphons that attach to your sink can be purchased. This type of siphon helps prevent water spilling outside of the bucket. Some siphons allow you to choose the suction of the water and the temperature when filling the tank.
  1. Clean the aquarium’s decorations.
  • Excess algae are caused by excess nutrients in the water. You can wipe the decorations off with an algae pad or a new soft-bristled toothbrush.
  • If you’re having difficulty cleaning the decorations, remove them from the tank and clean them in the tank water you siphoned out. Avoid the use of soap or other detergents.
  • If you’re still unable to clean them properly, soak the items in a 10% bleach solution for 15 minutes. Then pour boiling water over them and let them air dry before placing them back in the tank. Be very careful to remove all bleach; bleach will kill your fish.
  • If your decorations are covered in algae, you may want to feed your fish less or change the water more frequently. Adding a pleco fish in larger aquariums can help prevent algae from growing excessively.
  1. Clean the gravel (substrate).
  • To clean gravel, push the vacuum through the substrate in your tank. Excess food, fish waste and other debris will be sucked into the vacuum.
  • With sand substrate, be careful not to use the vacuum like a shovel. Use just the hose part of the siphon, under an inch from the surface to suck up waste without disturbing your sand. Use your fingers to run through the sand, if there are no buried animals, to help debris float up to the top.
  • Place a never-worn stocking over the end of the siphon to avoid harming very small, weak or delicate fish.
  1. Add fresh water.
  • Replace the water you took out with fresh, treated water at the temperature of the aquarium. A significant change in temperature will kill your fish. To be safe, always test the water before adding it to your tank.
  • A thermometer is the only way to verify the temperature. Staying inside the dictated temperature for your species is essential for the health of your fish.
  • If you use tap or well water, you must condition the water to remove heavy metals and other toxins. For tap water, select a container that is designated only to your water changes and fill it up the day before. Leave the water uncovered so the chlorine can evaporate in 24 hours.
  • If you are not able to prepare tap or well water in advance, use a decolorizer. Another option is to use bottled spring water for water changes (with no conditioner) because this water has none of the bad elements.
  • Do not fill up the water to the top of the tank. Fish need some space between the water and the top so that they have enough oxygen-carbon dioxide exchange to breathe.
  • If the nitrates are exorbitantly high, perform a special water change of 50 to 75% distilled water. This should not be a regular task.
  1. Add aquarium salt.
  • Freshwater aquarium salt provides electrolytes for the fish and helps to prevent diseases such as ich (Ichthyophthirius multifiliis).
  1. Watch the water.
  • The water will become cloudy. Wait a few hours for the cloudiness to dissipate, leaving the water sparkling clear.
  • If the water remains cloudy, you need to identify the underlying problem. Using a clearing agent will not solve the issue.
  1. Clean the exterior.
  • Wipe down the outside, including glass, hood, light and tank top.
  • The ammonia fumes from standard cleaners can hurt your fish, so only use solutions that are designated as aquarium-safe.
  • If you prefer to make your own cleaner, you can use a vinegar-based solution.
  1. Change the filter cartridge once a month.
  • The carbon inside of the filter cartridge can become harmful to your fishes’ health if not regularly changed.
  • A small amount of beneficial bacteria lives inside the filter, but most are in the gravel, so changing it will not affect the biological filtration.
  • The cartridge can be rinsed off weekly when water changes are performed if it appears to be excessively dirty, but you don’t want to lose the beneficial bacteria that live in the filter. Rinsing the filter cartridge does not substitute for changing it monthly.
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