Skip to Content

8 Crystals To Keep In Your Aquarium!

The popularity of crystals amongst Millennials and members of Gen Z has been increasing for over a decade now so it is not surprising that we have noticed a number of people asking about keeping crystals in their aquariums.

We have seen a range of questions about the various crystals that can safely be kept in an aquarium recently so we have decided to publish our own dedicated article going over the subject.

Now, just because some crystals can safely be kept in your aquarium, it does not mean that they are safe and suitable for use with all types of fish.

Some crystals are also classed as being safe for use in your aquarium too but in reality, they do increase the amount of tank maintenance required on your part to keep the water conditions optimal and free from toxins so you do have to factor in things like that too.

As we work our way through our article, we will be going over the various factors that you have to consider when adding the suitable crystals to your aquarium.

On top of that, we will also be touching on a number of crystals that should be totally avoided when looking for something for an aquarium with fish or other live animals or plants in it too.

Can Crystals Go In A Fish Tank?

Although there are a number of crystals and polished rocks that people do add to their aquariums and fish tanks, there are a number of variables that you have to factor in prior to adding the crystal to your tank.

For example, some options are safe for tanks without any bottom-dwelling fish but will cause problems if your tank has a bottom dweller in it.

Some crystals can also cause problems with the water conditions too so you have to keep that in mind for sensitive fish such as bettas too.

This is why we usually just recommend that our readers go with fake aquarium crystals if possible as it avoids the majority of the trouble required for matching the perfect crystal to your aquarium.

Another option that some people do use is to use a crystal substrate for their aquariums but this is not suitable if you have bottom-dwelling fish or scavengers.

That said though, we know that some of our readers will still want to be using actual crystals for their aquariums so we will be going over our best options below.

If you are planning to add crystals to your aquarium, please be sure to clean it correctly prior to putting it in your tank too as this will help to reduce the risk of contaminants making it into your tank.

What Polished Rocks And Crystals Are Safe For Aquariums?

Crystals such as amethyst, citrine, ametrine, smoky quartz, granite, jasper, agate, and jade are usually suitable for the majority of aquariums and fish tanks.

This selection of crystals should allow you to match up a range of different colors to get the exact look and feel you want for your aquarium layout with ease.


The most commonly used crystal in aquariums has to be Amethyst with it being one of the better crystal options for an aquarium.

Amethyst does present a scratching hazard for some fish depending on your tank layout and it can start to fade in color quickly under certain fluorescent lights but thankfully, it is cheap and easy to replace once the color of the Amethyst starts to fade.


The use of Agate as a crystal in an aquarium is becoming more and more popular due to Agate not presenting as many potential problems as some of the other crystals out there.

That said though, you should never put Agate into a tank with bottom-dwelling fish as it can scratch them with ease.

One of the main selling points of Agate is that it is cheap and available in mixed color packs to add some variety to your aquarium but it is also available in single color packs with Red Agate and Purple Agate usually being the more popular options for aquarium use.


Although some people do add Citrine to their aquariums, it is controversial due to real Citrine getting its from iron and some Citrine products not sealing the crystal prior to selling it.

This means that the iron can then come off the Citrine once added to your aquarium and cause pollution and toxin issues with your aquarium water.

It is also surprisingly difficult to find aquarium quality Citrine but some people will just use regular Citrine and accept the risks but we usually recommend against this.


Actual Ametrine is another popular crystal that some people keep in their aquariums.

You can sometimes find aquarium grade Ametrine that has had the rough edges smoothed off as well as a sealant applied to the crystal to prevent any potential issues but it is difficult to find Ametrine in this state.

Some people do just use tumbled Ametrine instead due to it being smoother but it does not have an aquarium safe sealant on it so may pose a potential risk to your fish.


There are a number of safe Quartz crystal types that are commonly used in aquariums with UU UNIHOM 1 lb Bulk Rose Quartz Rough Stones - Large 1" Natural Raw Stones for Tumbling, Cabbing, Fountain Rocks, Decoration,Polishing, Wire Wrapping, Wicca & Reiki and Smokey Quartz being the two most popular options by far.

Although both types of quartz can work well in some aquarium setups, you really do have to take the time to ensure that you are cleaning the Quartz crystals correctly before you add them to your aquarium.


Although Granite crystals is usually the best option to keep in an aquarium due to Granite usually being an inert crystal that should have no effect on the water conditions in most aquariums, many people think it is a boring option and avoid it.

Granite can usually be found cheap making it a very budget-friendly too with it usually being easy to find while also requiring minimal preparation or cleaning before you add it to your aquarium.


The popularity of using Jasper as a crystal of choice for aquariums has been increasing over the last year or so with Red Jasper being an excellent option for aquariums. On the flipside of this though,

Rainbow Jasper has a huge amount of metallic impurities in it and will often cause issues with the water quality of your aquarium so only stick to Red Jasper.


Both actinolite and jadeite Jade crystals are commonly kept in aquariums with there being some rare issues with using Jade as your crystal of choice but it really is very rare that you will have issues.

In that rare situation where you think that your Jade crystal is causing potential problems with your water quality then you should remove the crystal immediately and correct the issues with you water quality.

What Polished Rocks And Crystals Should You Avoid In Your Aquarium?

You should usually avoid any crystals or polished rocks that have a large amount of aluminum in them and keep them out of your aquarium.

This includes Emerald, Garnets, Labradorite, Moonstone, Ruby, Sapphire, Topaz and Turquoise. Additional crystals that should be avoided include Lapis Lazuli, Bumblebee Jasper, Malachite, Sulphur, Brimstone, Tiger Eye due to the asbestos and sulfur content as well as lava rock, coal, limestone, and dolomite.

Although there are reports on social media of people being able to keep pretty much all of those options in their aquariums, we would highly recommend you avoid taking the risk.

They all pose a potential thread to your fish due to being able to quickly change the water quality in your aquarium with the risk simply outweighing the reward of their unique looks.

Just try to stick to the safer crystal options covered earlier in the article for use in your aquarium as they still look good but have a much lower risk of contaminating your water quality.

Keep in mind though that we actually recommend against using any crystals with your aquarium as the majority of them do pose some sort of a threat even if it is minimal.


That brings our article going over using crystals in your aquarium to an end. We hope that we have been able to help you identify the crystal options that can be used in aquariums with minimal risk as well as the ones that you should outright avoid. Keep in mind that just because a crystal is considered to be aquarium safe, it can still pose a threat to your fish due to being a scratch hazard, particularly for bottom-dwelling fish.