Can You Put Seashells in a Fish Tank? Is It Safe?

Alison Page

Alison Page


can you put seashells in a fish tank

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Your aquarium is not only a perfect habitat for your fishy friends, but it’s also a visually pleasing focal point in any room.

Most fish keepers like to enhance the look of their tanks by using various decorations and live plants, and these additions can provide hiding places and shelter for shy species of fish, too.

Popular tank decor includes rocks and driftwood, but can you put seashells in a fish tank?

The good news is that you can use seashells in a freshwater aquarium and saltwater setups with a few caveats without harming your fish.

That said, seashells can change the water chemistry over time and might come with a few unwelcome hitchhikers in the form of bacteria and parasites, which you’ll need to remove before you use the shells in your tank.

Read this guide to learn more about using seashells in a fish tank.

Can You Put Seashells in a Fish Tank?

Seashells on the beach sand

Seashells come in myriad different shapes, sizes, colors, and intricate patterns that can look truly beautiful when displayed alongside plants and brightly colored tropical and saltwater aquarium fish.

On the face of it, aquarium shells can seem like a perfectly natural item of decor for aquariums, but are they safe to use?

The first thing to know about decorating your tank with shells is that natural seashells will eventually alter the water chemistry in your setup.

Water Chemistry in Your Freshwater Fish Tank

Seashells and limestone rocks are composed of a combination of magnesium carbonate and calcium carbonate, primarily CaCO3, which is insoluble in water if the pH level is 7.0 or higher.

However, delicate shells will gradually dissolve in acidic water because the carbonate reacts with water to form calcium bicarbonate or CaHCO3, which is water soluble. When that happens, the water is neutralized, and the concentration of calcium in the water increases.

That’s why limestone or crushed clam shells are often used in a substrate to buffer the water pH. It’s important to remember, though, that since the seashells will slowly dissolve, the general hardness of the water or GH will gradually increase. Therefore, if your water pH is already high, say 9.0, adding a few seashells to the environment won’t make a lot of difference to the water chemistry.

Problems can occur if you dose your tank with CO2 for your living plants since the tank pH is lowered, resulting in a much higher dissolution rate for the seashells.

Using Seashells in a Saltwater Fish Tank

Roughly the same is true when using seashells in a saltwater fish aquarium, except that the target pH for a marine setup is generally around 8.2 to 8.4.

So in a saltwater tank, seashells won’t dissolve anywhere near as much as they would in a tank with a pH of 7.0 or less.

Invertebrates and Corals

Calcium is essential for the health of shells and coral skeletons, so if you keep a reef tank, using shells can help to keep the environment healthy for your livestock.

That said, it’s important that you also use a calcium supplement that’s specifically designed for use in aquariums to ensure accurate dosing.

Where To Use Seashells

So, if you keep a Rift Lake or marine aquarium, using real shells is fine since you want alkaline water and a high pH.

However, if you keep types of fish that need soft water conditions and prefer neutral or low pH and acidic water, such as angelfish or discus, using too many seashells might not be such a good idea.

Why Use Seashells in Your Fish Tank?

You might want to use seashells in your fish tank for several reasons.


Seashells are beautiful objects that can really enhance the look of your fish tank and allow you to create a fantastic underwater landscape with an ocean theme.

If you keep a marine or reef tank, seashells can add a wonderful natural vibe to your aquascape that sets your fish off beautifully.

Creates a Natural Habitat

Although kids and teens often like to create somewhat off-the-wall themes for their fishy friends’ tanks, many other hobbyists, including me, prefer a more natural look for the habitat.

can you put seashells in a fish tank

Seashells can go a long way toward replicating coastal, brackish habitats, where you often find seashells. This can help to make the fish feel safe, secure, and more at home, potentially reducing stress and encouraging natural behaviors, such as foraging and exploring.

Mark Out Territories and Provide Hiding Places

If you keep territorial, larger fish species, you can use strategically positioned seashells to mark out areas your fish can adopt as territories, which can help to reduce aggression and create harmony in a community tank.

In addition, shy fish can use large shells as a refuge when they feel threatened, and shells can provide nocturnal fish with hiding spots where they can safely rest during the daytime.

Drawbacks of Using Seashells in an Aquarium

Of course, there are also a few downsides to using seashells in your fish tank, including the following.

Water Chemistry Alterations

As mentioned above, under the right conditions, seashells can release calcium and carbonate ions into the tank water, which can eventually change the water’s pH levels.

Some fish species from soft-water environments might be sensitive to those changes, which could lead to health and stress issues. For that reason, you must research your fish species’ specific needs before adding seashells to your aquarium.

Injuries To Fish

Seashells that you find while beachcombing often have jagged edges or rough surfaces that might harm your fish and other aquatic life, especially if you keep species with trailing fins and delicate scales.

In addition, if the fish rub against rough shell surfaces, they can sustain injuries that might result in infections and even death.

If you decide to use natural seashells, remember to check them carefully to ensure they’re safe for your fish.

Bacteria and Pollutants

Many seashells’ crevices and patterned surfaces can provide an ideal environment for various types of bacteria and other microorganisms to grow and trap organic matter that could harm your fish and impact water quality.

That means you’ll need to thoroughly clean the shells before introducing them to your tank to prevent the risk of fish mortality.

How To Clean Seashells

Seashells contain many different types of marine bacteria and often contain tiny scraps of the previous inhabitant, which could harm your freshwater fish.

Although you can clean natural decorations with a weak bleach solution, using a steam sterilizer to kill the bacteria is just as effective and safer for your fish. If you know someone who has just had a baby, they will probably have a steam sterilizer that you might be able to borrow.

Alternatively, you can boil the seashells thoroughly for at least 10 minutes to kill off the bacteria. However, you’ll also need to use tongs to remove any fragments of organic matter that could be lurking deep inside the shell before adding them to your aquarium.


Once you’ve finished preparing the shells for your fish tank, you can take steps to prevent the shells from decomposing and affecting the water quality by painting them with an aquarium-safe varnish designed specifically for fish tank decorations.


If you don’t want the hassle of cleaning and prepping shells from the beach, you could buy them from your local fish store instead.

Often, fish stores stock a small selection of clean, sterilized, and tank-ready seashells. These perfect shells can be put straight into your tank once you’ve rinsed away any shelf dust and debris, saving you a whole lot of time and effort.

That said, I recommend you still inspect the shells carefully to be sure they’re smooth and free from sharp edges to prevent injuries to your fish.

If you would prefer not to use regular shells, plenty of resin replicas look pretty convincing and are totally safe for use in your aquarium.

Final Thoughts

I hope you enjoyed our guide to using seashells in your fish tank. If you found the information helpful, please take a moment to hit the share button above!

Although you can use the seashells that you find on the beach in your fish tank, it’s essential that you clean them thoroughly first to kill any bacteria that might be lurking in the crevices on the shell’s surface.

In addition, if the pH in your tank is acidic, the shells will gradually dissolve, releasing several types of minerals into the water, and rough or sharp surfaces could injure vulnerable fish.

Do you keep natural seashells in your aquarium? Tell us in the comments box below.

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