How To Make Aquarium Decorations Safe For Your Tank

We spend a lot of time and money on our aquariums. 

Not only that, but we have a lot of emotional investment in our tanks and want to know that the decorations we use will not harm our fish or invertebrates.

When it comes to making aquarium decorations safe for use, there are two main things to worry about: making sure the decor is sanitized and ensuring there are no sharp edges that can harm fish as they swim by.

Today, I’ll go over some basic steps that you can use to make sure your decor is safe for use.

How to Make Aquarium Decorations Safe

Let’s go through the steps you can take to ensure decorations are aquarium safe.

Sanitizing Rocks, Resin Decor and Other Hardscape Pieces

Aquarium decorations you buy from the pet store should be safe to use without major cleaning. Maybe just rinse them off with regular tap water to clear away any dust that may have settled on them.

But, if you want to use rocks you found in nature, or if you have doubts about the cleanliness of decorations, it’s best to sanitize them to make sure they’re safe.

I don’t mess around when it comes to sanitizing aquarium hardscape. If I think anything might be questionable, I break out the big guns and sanitize everything with bleach.

Don’t use this method on silk plants or any decoration that incorporates some kind of cloth. Bleach will strip the color out fabric decorations.

To sanitize aquarium decor with bleach, you’ll need:



  1. Make sure that you only use plain bleach. DO NOT use scented or “splashless” bleaches. These have additives that can leave harmful residues. Get the old school, cheap bleach that’s just made out of sodium hypochlorite.
  2. I highly recommend that you carry out these steps in your bathtub or shower, and make sure to wear old clothes you don’t mind staining with bleach.
  3. Mix up 1 part bleach to 20 parts water. So, for example, if you use 1 cup of bleach, you would need 20 cups (5 quarts/1.25 gallons) of water. Mix up enough diluted bleach to fully submerge the item(s) you want to sanitize.
  4. Let the decor soak for several minutes. You can let items with stubborn algae or stains soak longer, if needed.
  5. Dump the bleach water and rinse the item(s) with tap water until you can no longer smell bleach.
  6. Fill the bucket with enough water to submerge the item(s) and add 4 times the normal dose of dechlorinator for that volume of water. Soak the item(s) for 10 minutes.
  7. Dump the dechlorinator water. The decor pieces should now be safe to place in the aquarium.

Never try to bake or boil rocks to sanitize them. This can heat up air pockets inside the rock, causing them to rapidly expand and blow the rock apart. This can cause serious injury and property damage, don’t risk it!

Sharp Edges

Another safety concern with decor items can be sharp edges. As fish swim by, or even into, decor, they may brush their face, sides or fins against the edges or corners of decorations.

Repeated scrapes can cause cuts and scrapes, leaving fish susceptible to infection because of these wounds.

It’s best to feel decor items all over with your hands to check for sharp edges. 

Run your finger around the inside of any cave openings. 

Resin decor in particular is notorious for having sharp edges around cave entrances. These can be very dangerous to fish, especially if they quickly dart through the opening in a panic.

You can use a fingernail file or fine tooth rasp to smooth out sharp edges on resin decor. This can require some patience, just stick with it until the edges are smoothed out. 

To test if the edges are safe for fish, you can do the “pantyhose test.” Basically, you stretch pantyhose material over your hand and run it over the decor edges.

If the pantyhose gets torn or frayed, the edges are still too sharp, you need to keep filing.

If you have particularly jagged or sharp rocks, you may consider not using those particular pieces and look for something a bit smoother. 

Always Substance Over Style

Keeping the livestock in our tanks safe should be a fishkeeper’s number one priority. So, it makes sense that you’ll need a way to ensure that your aquarium decorations are clean and safe for use.

Sanitizing with bleach may seem like overkill, but it’s the most effective way to make sure that no harmful pathogens hitch a ride into an aquarium.

As well, filing down sharp edges can help prevent injuries that make fish susceptible to disease. 

If you can’t readily smooth out sharp edges on a piece of rock or decor, it may be worth it to exclude it in favor of a safer alternative.

I’d rather lose out on some money for a decoration, rather than lose a fish.

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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