How to Remove Hard Water Stains from Aquarium?

How to Remove Hard Water Stains from Aquarium?

Hard water stains are basically mineral deposits that not only make your fish irritated; moreover, it’s also unpleasant to look at. Although, to make it clear form beginning that these residues are not harmful to your fish, but it only makes it difficult for the fish to see their food or other stuff.

Although, these stains are harmless to your fish most of the beginners make it dangerous for their fish while cleaning. As you see these blurry hard stains over your aquarium glass you urge to use household cleaning stuff like chemicals etc. once even the slightest amount of these chemicals is left in your aquarium it can prove deadly for your fish.

In this article, we will discuss the nature and formation of these stains and the methods to prevent it and methods to clean it. We hope this article will help you in future.

What are hard water stains?

As we already know that water hardness ranging from 2-25 dGH is most preferred for a wide range of fishes. Over time as this hard water evaporates, its lighter particles evaporate in the air leaving behind the heavy and hard particles.

 As these particles accumulate, they stick with each other and with the clear glass surfaces. After some time, you begin to notice white spots or blotches all over your aquarium glass. Basically, these stains are calcium carbonate or commonly known as limestone.  

These stains get whiter with time and make your fish tank look ugly. Harder the water, greater the amount of minerals in it, more the formation of white spots.

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How to remove hard water stains?

In order to get rid of these stubborn stains, your priority should use fish-friendly detergents or soaps. Normally, while cleaning the tank it is recommended to avoid using harmful detergents or chemicals. Fish safe cleaning sprays are easily available at pet stores; moreover, they are affordable and handy to use.

Following steps should be taken to effectively remove these stains from your aquarium walls.

  1. Remove your fish from the tank and place them in some safe holding tank.
  2. Secondly, remove the decoration and equipment cleaning them as well if needed with algae removing scrub or normal brush.
  3. Now empty the tank, remove all the water and rinse it well.
  4. Afterwards, there are two most widely recommended products to use. First, use fish-friendly sprays or use normal white vinegar.
  5. White vinegar is a great disinfectant and is believed to be pretty effective against limestone. When vinegar reacts with calcium carbonate, vinegar disintegrate the deposits of limestone, dissolving them. Moreover, vinegar is harmless to your fish.
  6. Now cover the whole tank with a sufficient amount of vinegar. Leave it on for 2-3 minutes. After this time use a simple scrub to clean it well.
  7. Now rinse the tank properly.
  8. After drying the tank with some towel to remove any remaining chemical.
  9. Fill the tank with clean water, add the equipment and decorations, before adding the fish use the water testing kits to ensure ideal water parameters and then add in your fish.
  10. The water cycles will get disturbed as a result of total water replacement from the tank. Thus, using store-made bacterial colonies to re-establish the cycles.
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Above-mentioned steps are the ultimate solution to hard water stain removal.

How to Prevent the Formation of Hard Water Stains?

As prevention is better than cure, thus, to avoid the formation of these hard water stains try to avoid mineral build-up. First of all, don’t use super-hard water as it contains lots and lots of minerals.

Furthermore, using distilled water is the best way to prevent these spots from forming. But using distilled water comes with the problem of lack of essential minerals. Thus, the best-recommended method is to make the hard water a little dilute. As the previous water evaporates leaving behind water stains, adding the same hard water will eventually lead to mineral over-build.

Thus, as the water evaporates fill it in with normal distilled water free of minerals. In this way, minerals will not accumulate and this diluted water will not form water stains.

Read Our Other Article On: What Is New Tank Syndrome? And How to Deal with It?


Although, these water stains are not dangerous or anything but they actually reduce the beauty of your tank by many factors. Preventing the formation of these minerals deposit is much easy than actually removing the stains.

I hope our article helped you in solving this annoying issue. Tell us in the comment section below if you face any other problem regarding your aquarium.

Learn more about aquarium care guides here.

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