Crystals in the Aquarium


I have had countless people ask me whether crystals and various minerals are safe in the aquarium. And the answer is a definite YES! I find these questions ironic as people will fill their tanks with neon and glow in the dark plastic, yet don’t think twice about that. Many people keep these decorations in their tanks for years (i’ve done it too) without considering the parameters the items were tested in that deemed them ‘safe’ in the first place. I mean your ph in your tank could be breaking it down even more then what was initially  tested for… and I doubt TopFin or Nat Geo let these decorations sit in a tank for years as their testing process before these products went to market. Also, there’s no such thing as non-toxic plastic. Its fucking plastic. It’s made of petroleum and it most definitely breaks down in water. Personally, I feel like there is enough plastic in the world and this is one area that can be avoided so easily. At the end of the day you should be concerned with anything you put into your habitat and try to keep it as natural as possible.


But, some people don’t really like the biotope look, they want something colourful. And crystals are the perfect answer to this. Not only are they beautiful and colourful, but they have healing and cleansing properties too.


Here’s some of my favs:


Amethyst-  high spiritual vibration and protective stone, blocks geopathic stress. Very calming for the mind


Citrine- energizing crystal, protects auras, grounds negative energy, promotes joy and happiness


Quartz- energy amplifier, regulates and stores energy, increases biomagnetic fields, stimulates the immune system, soothes burns


Agate- eliminates negative energies, aids digestion. Promotes love and affection.


Labradorite- deflects unwanted energies, relieves stress, lowers blood pressure and balances hormones.


White jade- directs energy towards goals , treats kidneys and removes toxins, aids fertility


There are some things that are bad for your fish. You can learn the signs to determine yourself, even if you don’t know what mineral it is specifically.



This is a huge no no. Some fish can handle small amounts but a lot of species like, ghost knife are very sensitive. This also means no malachite. Copper can can look like Brown spots so avoid anything with copper hues.


Other heavy metals:

There’s a few out there so look for anything hard and shiny, like hematite. Apparently this goes for pyrite as it is also a metal. But in moderation I think pyrite is fine. I have a piece in my tank mixed with granite so it’s not as pure and it has been fine.


Water soluble/ soft minerals:

From my research I have learned that calcite and fluorite are dissolvable in water and therefore aren’t good. I suspect that any soft stone like selenite, tourmaline or rock salt are also not going to work as they will definitely break down in the water. The same goes for Limestone as it is also very soft.


Anything that looks flaky:

Stones like Gypsum or sugarlite are a no-go. Any patches of brown crumbly bits are signs it’s too soft for the aquarium.


What to look for:

More opaque is better. Pure crystals like Quartz and its variations are best. Quartz comes in a lot of forms like granite or agate so there’s lots of colours and options out there. You can always look up a mineral and see if it has a high mohs value and is considered a hard stone.


Whether the stone dissolves in the tank actually depends on the acidity aka the PH you keep. So if you run your tank on the acidic side then stick to very hard stones.


When In doubt, test it!


I realize most people don’t have a heavy metal test kit so here’s some solutions you can use to problem solve.


I recently read about a vinegar test. Add some vinegar to your stone and watch for bubbles. This means it’s reacting to something like calcite, which is in a lot of stones.


But, calcite isn’t really the concern with high quality crystals. This could be more of a concern for rocks you found on your own.


For crystals, you could soak it in some water and then ask your local pet store if they can test that for you. In general though, I suggest letting a new crystal soak in some tap water for 12+ hours and then test the ph, gh  and kh (compared to tap water).

If you don’t trust me. Then do some research online yourself before adding something sketchy to your tank I hope you all enjoyed this post and feel inspired to class-up your tank with crystals! And yes, they are expensive compared to pet store junk, but you get what you pay for. These beautiful pieces will last the rest of your life and took millions of years to create. I get so bored of seeing the same old grey dragon stone people use in literally every scape! Get creative and match the colour scheme of your home as I’m assuming it’s not all grey :p  I live in the Pacific northwest so I get enough grey in my life… we don’t see the sun for weeks at a time so my crystal collection helps keep me cheery when I can’t go out and connect with nature and I think my fish appreciate it too! Check out our ‘decoration’ section in products for some amazing crystal deals on small medium or large pieces.

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