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How to Clean Hard Water Stains in an Aquarium

By Jen Davis

Photodisc/Digital Vision/Getty Images

Hard water stains can develop in your aquarium if you use water with a high mineral content to fill your tank. These stains can make it difficult to see your fish through the glass, as well as cause your entire tank to appear discolored. You can remove hard water stains by properly cleaning the glass in your aquarium.

Step 1

Remove all your fish from your tank by scooping them out of the water with your net. Place the fish in your backup aquarium, where they can safely reside while you clean the hard water deposits off your primary aquarium.

Step 2

Scrape off as much of the hard water deposits as you can with your aquarium scraper.

Step 3

Mix half a cup of white vinegar with a gallon of water and pour the mixture into a spray bottle. Spray on the deposits and then scrub them away with a washcloth.

Step 4

Rinse fish tank thoroughly with clean, fresh water. Make sure to completely wash away all possible traces of vinegar completely from the tank. Refill your tank with clean, fish-safe water and return your fish to their newly cleaned tank.

Items you will need

  • Aquarium scraper
  • Washcloth
  • White vinegar or commercially available fish tank cleaner
  • Spray bottle
  • Net
  • Spare aquarium
  • Fresh water for your tank


  • 💡 You can use commercially available fish tank cleaning products to clean your fish tank in place of vinegar. Make sure to completely and accurately follow the directions on any products you use.


  • Never use window cleaner or other chemicals in your fish tank because even the slightest chemical residue left behind can sicken or kill your fish.

Photo Credits

  • Photodisc/Digital Vision/Getty Images


Jen Davis has been writing since 2004. She has served as a newspaper reporter and her freelance articles have appeared in magazines such as "Horses Incorporated," "The Paisley Pony" and "Alabama Living." Davis earned her Bachelor of Arts in communication with a concentration in journalism from Berry College in Rome, Ga.