Can you reuse aquarium gravel? Is it safe?

Last Updated on August 27, 2022 by cmoarz

It’s time to change your aquarium gravel again! What a pain! But should I really buy new gravel or can you reuse aquarium gravel?

In short, Yes you can reuse your old aquarium gravel. Buying gravel over and over again is expensive so why do it? Save your money and check out the instructions below.

Instructions for reusing aquarium gravel

  • Collect the gravel from the dirty tank and place in a 5 gallon (ca. 19 l) bucket or large strainer
  • Run it under hot water and agitate aggressively with a stick to remove particles
  • Rinse and repeat at least twice or until water runs clear
  • Now bring a pot of hot water to boil and add your cleaned gravel
  • Keep at a high boil for at least 10 minutes
  • Let the rocks cool down, They will retain heat for some time.
  • That’s it! You should do this before adding new gravel into a tank as well.

Read our post on boiling aquarium gravel which answers common questions you might have.

Why is it important to sterilize before reuse?

For new gravel it’s important to remove left over dye, powders and other contamination that may be attached to the rocks.

You wouldn’t want to add your nice new blue gravel into your fish tank and it turns the water a dark blue, would you?

So washing and sterilizing new gravel is important.

For old and dirty gravel I think the answer is obvious, It’s dirty! Covered in fish defecation, decomposing fish food, all sorts of bacteria and other growth (good bacteria too, But if its been sitting a while you definitely want to clean it).

What happens if you are going to add your old gravel to a new tank but there’s a slime mold growing on it? Well your new tank is now screwed!

Let me ask you this, When you go to a restaurant you expect the forks to be clean? Would you be ok with sharing forks with everyone that was in the restaurant that whole day?

Of course not!

Your fish feel the same way trust me. Be nice, Be kind. Save some money and save some TIME!

Whats left behind on my used gravel?

Well if my above description wasn’t enough, let’s take a look at some things that can grow on aquarium gravel. Remember, while you are looking threw these images, it’s easier to avoid these things than to fix them.

Brown Diatom Algae

An image of brown diatome algae in a fish tank
Image source

Not all algae are bad, Brown Diatom for example is wanted in many because the tank critters love to eat it. Shrimp, Snails, etc. They love the stuff and can’t get enough.

But if you have a tank species that doesn’t eat this stuff it’s bad! It looks terrible and dirty, and gets everywhere.

If you don’t clean your gravel, these spores can attach to the rocks and transfer to any new tank you get. Good luck removing it without cleaning and changing everything.

Black Beard Algae

An image of black beared algae infesting an fish aquarium
Image source

This stuff is super common and also super hated. Not many animals eat it so it’s pretty worthless, especially in your tank.

If you have any of this stuff left over on your gravel, it’s going to rapidly reproduce until your entire tank is nothing but a giant “beard” of algae.

It’s not easy to remove once it takes root either. That’s why sterilization of the entire tank and everything in it is so vital and important.

So, Can you reuse aquarium gravel? Absolutely. Just remember to clean and sterilize it first!

Don’t forget to check out our other articles:

Is colored aquarium gravel safe?

How to remove tannins from aquarium water

Picking the correct aquarium gravel

Why should I use aquarium gravel?


Owner of and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!