How to Clean Fish Tank Rocks (3 Proven Methods)

I have three basic methods I use for cleaning aquarium rocks: vinegar method, peroxide method and bleach method.

Vinegar is great for rocks that just have a little algae build up, but not really any staining. It’s acidic and will help break down soft algae quickly.

Peroxide is a strong oxidizer that can usually clean off fairly medium toughness algae, like green beard algae.

But, if all else fails, I reserve bleach for the toughest cases, like green spot or black beard algae. 

You have to be more cautious with bleach than you do with vinegar or peroxide. You’v got to try to prevent spills, try not to get it on your clothes and you’ll need to use a dechlorinator to make sure you get rid of it completely. 

But, it will take off just about anything.

Never, ever wash aquarium rocks with soaps or other detergents. These can leave residues that are highly toxic to fish. Also, make sure that any buckets or scrub brushes you use for cleaning your aquarium have not been used for household cleaning, as residues can coat brush bristles and bucket walls, even if they’ve been washed.

1. Vinegar Method


  • Vinegar – I use either white or apple cider vinegar whichever I have on hand.
  • Empty spray bottles
  • Scrub brush with plastic bristles
  • Tap water


  1. Remove the rocks from your aquarium.
  2. Fill the spray bottles with a 50/50 mixture of water and vinegar.
  3. Spray to thoroughly coat the rocks in the vinegar mixture. Let sit for 5 minutes.
  4. Scrub the surface vigorously with the brush and rinse with water. Repeat as needed.
  5. The rocks are safe to be put back in the aquarium after a good rinsing.

2. Peroxide Method


  • 3% hydrogen peroxide – just the normal stuff from the drugstore is fine.
  • Empty spray bottles
  • Plastic bristle scrub brush  


  1. Fill the spray bottles with hydrogen peroxide.
  2. Remove the rocks from the aquarium.
  3. Spray peroxide all over the surface of the rocks and allow it to foam for about 30 seconds.
  4. Scrub the rocks with the brush and continue to let it foam up. You can add some more peroxide if the foaming has died down.
  5. Rinse the rocks in cool tap water and repeat spraying and scrubbing if needed.
  6. The rocks are safe to put back in the aquarium after a thorough rinsing with tap water.

3. Bleach Method

I reserve this for the most stubborn stains and algaes, green spot is the most likely culprit to require bleach.

I know some people might be wary of using bleach for their aquarium rocks, but I assure you, I have used this method dozens and dozens of times on my own aquarium equipment and decor over the years.


  • Plain bleach – must contain only sodium hypochlorite. DO NOT use “splashless” or scented bleaches. These contain additives that can leave toxic residues on your rocks. Cheap, old school bleach is what you need.
  • Buckets
  • Tap water
  • Dechlorinator – I prefer Seachem Prime because it is highly concentrated.


  1. Remove rocks from your aquarium and place them in buckets. Bleaching rocks is best done in a bathtub or shower. Make sure to wear clothes you don’t mind getting bleach on. 
  2. Mix 1 part bleach to 20 parts tap water. That comes out to roughly 6.5 fluid ounces per gallon.
  3. Submerge the rocks in the bleach solution in your buckets for several minutes, then pull them out and give them a quick scrub.
  4. Place the rocks back in the bleach solution for another 10 minutes or so.
  5. Usually, at this point, all the algae and stains have been removed from the rocks. If this is not the case, scrub and soak again.
  6. Once the rocks are clean, dump the bleach solution and rinse the buckets and the rocks with tap water until you can no longer smell bleach. 
  7. Place the rocks back in the buckets and cover with clean tap water. Add a 5 times the normal dose of dechlorinator to the water and let the rocks soak for about 10 minutes. This will clear away any lingering bleach residue.
  8. Dump the water and the rocks are now safe to put back in the aquarium.

Final Thoughts

Algae and biofilm can really build up and begin to stain aquarium rocks, just making the tank look a bit dingy.

Luckily, there are lots of options out there to clear up all that gunk from your fish tank rocks.

Most of the time, vinegar or peroxide is all that’s needed to get them squeaky clean.

But, if something is just stubbornly stained, I highly recommend bleaching it.

I’ve used all of these methods more times than I can count. It’s always nice to clean up the algae and make it look like a whole new hardscape in the tank.

I hope you find this article helpful.

I wish you and your fish the very best!

Katherine Morgan
Katherine Morgan

Hey, there! I'm Katherine from Northwest Florida. An aquarium specialist, I've kept tanks for over two decades, enjoy experimenting with low-tech planted setups and an avid South American cichlid enthusiast.

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