How to Remove Hard Water Stains From Fish Tanks

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Things You'll Need

  • Aquarium razor scraper

  • Vinegar

  • Bucket

  • Squirt bottle

  • Hand towel

  • Bath towel


Vinegar can alter the pH balance of water. Test the pH balance before reintroducing your fish into the tank.

Only use rubber aquarium razor scrapers on acrylic tanks. Metal razors will permanently damage the acrylic.


On glass fish tanks, you can scrape away hard water stains with a metal razor blade.

Adding lemon juice to the vinegar mixture can help to mask the vinegar smell.

A clean and clear fish tank adds beauty to any room. Unfortunately, even with proper care, hard water can accumulate, leaving your fish tank stained and dirty. While removing hard water stains from your fish tank might seem like a daunting task, with the proper tools and a little bit of elbow grease, you can have your tank looking as good as new in no time.

Step 1

Scrape away large areas of hard-water stains with your aquarium razor scraper. You do not need to remove your fish while scraping the tank.

Step 2

Remove all fish and decorative items from your fish tank and empty out the water. If your tank decorations also have hard water deposits, place them in a bucket filled with 2 parts vinegar to 1 part water and allow them to soak while you clean your tank.


Step 3

Mix 2 parts vinegar and 1 part water directly into the empty fish tank. The amount of vinegar and water you use will depend on the size of your tank. For smaller fish tanks, apply the vinegar mixture directly onto the hard water stains using your clean squirt bottle. Let stand for 10 minutes.

Step 4

Scrub the sides and bottom of your fish tank with a hand towel. Rub vigorously in a circular motion. Run your toothbrush along the corners of the tank and around the edges to remove the hard water stains. Clean tank decorations by scrubbing with the toothbrush. Empty dirty water from the fish tank.

Step 5

Rinse your fish tank and decorations thoroughly with clean water. Towel-dry and reassemble your tank.