How To Remove Hard Water Stains From Fish Tanks?

Fish can have a healthy and happy habitat if their fish tanks or aquariums are well-maintained. You can achieve a clean and clear fish tank if you take care of them properly to avoid the accumulation of hard water stains. Stains can make your fish tanks dirty and unpleasant both in appearance and feel. With proper tools and other hard water stain remover products, you can have good fish tanks.

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What Are Hard Water Stains?

Hard water stains contain calcium and magnesium ions. It has a higher mineral content than others. Its appearance looks like a white chalk residue which is commonly noticed throughout your home. Hard water stains are formed because of the magnesium and calcium that leaves marks on surfaces. Hard water stains are mostly seen in bathroom tiles, glass surfaces, dishes, clothing, and other metal surfaces.

Things To Consider In Removing Hard Water Stains From Aquariums

Fishes prefer to live in hard water as their habitat. If you have noticed some white residue forming on the top of the glass, these might be a stain starting to build up in your fish tanks. Some items you need to remove hard water stains are vinegar, cleaning rag and aquarium scraper or algae scraper.

Here are some steps on how to get rid of unpleasant hard water stains:

Prepare The Materials

Prepare fishnets, clean buckets, clean cloth, cleaning rags or algae scraper, water, and vinegar. Unplug all electrical accessories of your fish tanks like heater, filter, and pumps. Remove all the fishes from the fish tank by using fishnet and place them in a clean bucket with water or if you have a spare fish tank, you may use it.

Mix Vinegar And Water

Mix 2 parts of vinegar and 1 part of water and directly pour it in the stained fish tank. Leave it for 10 to 15 minutes. If the fish tank is larger, double the mixture and if the fish tank is smaller, use a bottle to mix water and vinegar to spray the mixture to the stains. The mixture of water and vinegar depends on the size of the fish tanks.

Rub To Remove Stains

After 10 to 15 minutes, start scrubbing the area of the fish tank with hard water stains. Scrape stains using an algae scraper or cleaning rag. Rub and scrape large hard water stains and other residues in the fish tanks.

If some of the aquarium decorations also have stains, soak them in a bucket filled with two parts of vinegar and one part of water.

Rinse and assemble

Remove the dirty mixture of vinegar and water from the fish tank. Rinse the fish tank and other aquarium decorations thoroughly with clean water. Using a dry and clean towel or cloth, wipe out all the excess dirt in the fish tank and reassemble the decorations.

Refill the tank

Refill the fish tank with clean and safe water and put back the fish and decorations in the newly cleaned fish tank.

Top 9 Best Products To Remove Hard Water Stains And Dirt From From Fish Tanks

Hard water stains might be harmful to the health condition of fishes. A lot of products are available in the market which you can use as an alternative in removing hard water stains.

Here are some product cleaners to help you get rid of hard water stains in your fish tanks without harming the fishes.

API Safe and Easy Aquarium Spray

How To Remove Hard Water Stains From Fish Tanks?

It is an economical trigger spray used for cleaning the inside and outside of the fish tanks. It removes white-chalk residue or crusty mineral deposits in fish tanks and even in filters and other aquarium decorations. After spraying this API Safe and Easy Aquarium Spray, it serves as a protective coating for glasses and acrylic fish tanks. It also promotes healthy bacterial growth and helps to control and cure fish diseases.

API Algae Pad

How To Remove Hard Water Stains From Fish Tanks?

It is a hand-held pad for glass and acrylic aquariums that helps to remove algae easily scrapes residues in glass fish tanks. It comes with a durable scrubbing pad with hand-held control to clean nooks and crannies. Before using, rinse it with water because it is not used for dry surfaces.

API Algaefix

How To Remove Hard Water Stains From Fish Tanks?

It controls the growth of algae in the fish tank or aquarium glasses, plant and other decorations. It is also used in fish ponds. It is a safe product to prevent algae from rapid growth which results in stains and dirt in fish tanks. It uses an all-natural and highly-concentrated bacteria to break down algae and fist wastes.

Aqueon Limescale Remover

How To Remove Hard Water Stains From Fish Tanks?

It has a non-toxic formula that effectively dissolves hard water stains on glasses like in fish tanks or aquariums. It helps to remove unwanted residue without the use of harmful household chemicals.  It is used on glass and acrylic fish tanks and it can also clean aquarium ornaments.

Ultimate Bio-Clean: Safe Hard Water Spot Stain Remover

How To Remove Hard Water Stains From Fish Tanks?

This product is used to shower doors, windshields, glass doors and windows, and metals. It is also used for fish tanks to remove hard water stains.

Neptonion Magnetic Aquarium Fish Tank Algae Scraper

This magnetic cleaner is solely used for glass tanks. This device helps to clean fish tank glasses by magnetizing from an outside pad to the inner glass. This product makes it easier to eliminate to remove dirt and clean the whole tank without causing harmful effects to fishes and to the water.

Tetra No More Algae Tablets

These tablets help to control the rapid growth of algae in your fish tanks which sometimes causes dirt and stains. This product leaves the fish tack with crystal clear water. It works in glass and acrylic fish tanks. But this is not to be used in fish tanks with live plants and not recommended for turtles.

Luigi’s Aquarium/Fish Tank Siphon and Gravel Cleaner

It is a handy siphon pump that helps you to drain and change the water in the fish tanks to avoid hard water stains. It is perfect for regular water changes and it has a sturdy one-way valve to improve suction. It also filters through the gravel using the attachment to suck up food and fish wastes.

Just make sure to follow instructions accurately. Do not use other household cleaners or products like window cleaner because it can cause harmful effects to your fish or it might die.

Also, make sure to only use new cleaning rags to avoid the contamination from your previous cleaning products and to avoid toxic chemicals from entering the fish tanks as you clean them.

Why Do You Need To Keep Your Fish Tanks Clean?

To make sure that fishes stay healthy and in a good condition, regular maintenance of fish tanks is essential to ensure that the fish tanks are always clean and in a healthy condition. Water in a fish tank can easily acquire harmful bacteria or diseases if it is not properly cleaned. Here are some reasons why cleaning fish tanks are very important.

  1. To maintain the nitrogen level in low concentration – the higher the concentration of nitrates, the more it can be harmful to fishes. If you change the water regularly, nitrates become less harmful to fishes.
  2. To remove other particles and organic compounds in the fish tank – fishes can be infected by harmful bacteria if organic matters are not removed in fish tanks like food wastes and plants. These organic matters can also cause stains in fish tanks.
  3. To maintain the temperature – Check the fish tank temperature daily.
  4. To provide clean and healthy water – It is recommended to replace 10% of the water in the fish tank every 3 or 4 weeks to maintain the cleanliness of the water and keep away from algae.
  5. To keep the plant in the fish tanks alive – If fish tanks are clean, the plant will also be healthy and alive

How to Prevent Hard Water Stain From Building Up in your Fish tanks?

The easiest way to prevent the build-up of hard water stains is by regularly checking the fish tank’s water line every two or three days. The fish tanks accumulate hard water stains because of the evaporation process. As the water evaporates, the remaining water in the fish tanks will become slightly harder.

Replacing the evaporated water is one solution to avoid the build-up of hard water stains. By using distilled water as a replacement of the evaporated water, it eliminates the risk of death of fishes. Distilled water is better than replacing it with regular hard water because it contains a higher level of some minerals.

Hard water stains do not only appear inside the fish tanks, but it can also be noticed outside the fish tanks caused by water dripping or water splashes. Hard water stains outside the fish tanks build up when it is not immediately cleaned by a clean cloth or towel. 

Hard water stains are noticeable when the fish tanks are glasses. There are cleaners bought in stores that are mild enough to use. It will not affect the fish if you use this chemical only in the outside of the fish tanks.

Frequently Asked Questions

Is it safe to use a chemical to clean stains?

It is not advisable to use any chemical to clean and remove stains in your fish tanks. There are recommended product cleaners to remove dirt and stains from fish tanks that are commercially available.

How much vinegar should I use to clean the fish tank?

You can directly use vinegar when cleaning but to prevent problems, you can miss vinegar and water with 1:1 or 2:1 ratio.

Can I use apple cider vinegar for cleaning?

Apple cider vinegar is frequently used for weight loss. But with its composition, it is also good for cleaning fish tanks.

Will vinegar kill the fish?

It could kill aquarium fishes when too much vinegar is used. It is better to dilute the vinegar with water to balance the acidity of the vinegar.

Is cleaning with vinegar safe for all types of aquariums?

Vinegar might not work for some aquariums for the cleaning process.

Can I use dish soap for removing stains in my fish tank?

Do not use dish soap when cleaning fish tanks because even if it is rinsed well, some residue of soap still sticks to the walls of aquariums or fish tanks.

What is other equipment to remove stains from the fish tanks?

It is recommended to use brushes to scrub off the stains. Be sure that the brush is new and unused.

How often should I clean my fish tank?

To maintain the cleanliness of your fish tanks, you can come up with a cleaning schedule to monitor your fish tanks. It is safe to change 25% of the water every week.

Aside from water evaporation, what causes stains in the fish tanks?

When the fishes are overfed, some food wastes are left as particles in the water that causes dirt in the fish tanks.

How to clean and remove hard water stains without killing fishes?

First, empty the tank then try to rub and scour the fish tank with salt or baking soda. You may use magnet scrubber which looks like a stamp. Put one magnet inside the fist tank and the other one on the outside. You move around the magnet outside and the magnet inside will easily move to scrub off algae and other stains.

How long to soak the stain if it was not removed after 15 minutes?

Try to soak the fish tank with vinegar and baking soda paste mixture overnight then rub vigorously in a circular motion.

Can I use vinegar on acrylic fish tanks?

Yes, soak it with vinegar and water mixture then use a razor or scraper to remove stains.

How to clean fish tanks with eggs in it?

You can go with the usual cleaning but avoid to clean in the gravel areas where eggs are laid and do not expose then in the air.


Cleaning your fish tanks is one of the keys to keeping the environment healthy for the fishes. Cleaning products to remove hard water stains from fish tanks are just in your households.

Especially when fish tanks or aquariums are glass, it easily builds up hard water stains because of the dissolved mineral in the water. As long as the water is regularly changed every two or three weeks, you can avoid the build-up of those white residues from hard water.

If hard water stains are removed, fish tanks will look as good as new and free from dirt.