How to Remove Old Coralline Algae


Coralline algae is often found stuck to the glass, rocks, plumbing and artificial plants in an aquarium. It is usually red in color and the fish in your aquarium will usually not attempt to eat it. When it dies, it turns white and becomes very brittle. Coralline algae does have beneficial properties and many hobbyists allow the algae to live in their aquariums. However, you can remove old coralline algae from your aquarium if it has overstayed its welcome.

Things You'll Need

  • Gravel Siphon
  • Clean cotton rag
  • Razor blade or old credit card
  • Bucket
  • Hot water
  • Salt
  • Cold Water
  • Scrub brush
  • Tooth brush

Cleaning Off the Glass

  • Clean your arm thoroughly with water. Avoid using soap as it could transfer to the water. If you have a deep tank and you feel you might get your armpit into the water, remove your deodorant. These chemicals can harm fish.

  • Siphon approximately 10 percent of the water out of the aquarium with a gravel siphon and a bucket. This prevents the water from overflowing as you place your arm into the water. Use a bucket dedicated for cleaning your aquarium.

  • Wipe the surface of the glass to remove any fresh algae growing. Use a clean dry cotton rag that has never been used to clean with chemicals. An aquatic sponge works as well.

  • Locate stubborn old Coralline algae on the glass. If you have a glass aquarium, place the razor blade at a 45-degree angle to the glass and scrape the old algae off the surface. If you have an acrylic aquarium or plastic aquarium use a plastic credit card or gift card instead of a razor. Continue scraping until you removed all of the coralline algae.

  • Drain the water from your bucket back into the tank.

Rocks and Artificial Plants

  • Fill a bucket with hot water and mix in ¼-cup of salt per gallon of water. Soak the large rocks and plastic plants in the solution for 15 to 30 minutes.

  • Remove the rocks and plants and place them in cool fresh water with no salt.

  • Scrub the plants and rocks with a soft bristle brush while the plants and rocks remain in the cool water. This will help to remove the old algae and salt.

  • Rinse each rock and plant off using fresh tap water.

Filter Tubes and Air Tubes

  • Turn off the filter and air supply system in your tank as you normally would when completing a routine cleaning.

  • Scrub the algae free from the tubes with a clean toothbrush or an aquarium safe scrub brush.

  • Turn the filter and air supply system back on. The filters will remove any floating algae from the water within a few minutes.

Tips & Warnings

  • If you have live plants in your aquarium, you cannot remove them and scrub them. Stock your aquarium with a few algae eating fish like Clown Loaches or Otocinclus catfish. A Plecostomus fish will work as well. This is also the best option for removing Coralline algae from the gravel substrate in the bottom of the tank. You should never remove gravel and scrub it clean because you will kill bacteria needed to keep the aquarium stabilized.

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  • Photo Credit Jochen Sands/Digital Vision/Getty Images
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