Quartz In Aquarium Safe? What About Other Crystals?

Last Updated on January 10, 2022 by cmoarz

Can you put quartz in aquarium safely? Will quartz rock in aquariums cause any issues with the water parameters or damage fish? And if Quartz is ok, how about other crystals? What kind of changes can you expect in the water quality?

Quartz is definitely a beautiful stone and I can see why people would want to use it within their aquarium habitat design and in an aquascape. With that said, It’s mostly safe but there are some things you need to be aware of before diving into the wonderful world of aquarium crystals.

Quartz Rock in Aquarium

For the most part, everything inside a Quartz rock is perfectly safe for your aquarium and your aquarium fish. There are some exceptions that we will get into that are very important to know before you add these rocks to your aquarium though.

One issue with quartz crystal rock is the copper content. Copper is fine for most species of fish, But for snails and shrimp and other gastropods and crustaceans, it can be a deadly poison and irritant.

The copper in the quartz crystals can also cause chemical reactions with certain types of aquarium medications. These aren’t usually harmful on their own, but they could cause an algae bloom which would need to be dealt with, and really is only an issue with certain medications.

With that said, There are types of quartz rock that have less copper than others. You can also use an aquarium-safe clear sealant (lacquer) on the rocks. So when picking out your quartz, keep these things in mind.

Quartz Is Harder Than Glass

Because quartz hardness scale is higher than glass (Quartz is a 7 on the MOHS scale, and glass is a 5.5 to 7) it can easily damage and scratch up your glass aquarium.

This is something to be aware of but is usually easy to counter by placing a buffer between the rock and the glass.

Consider using sand or other types of aquarium gravel as a layer underneath the quartz, and try to stack quartz in the middle of the tank rather than up against the glass, Unless you have some way to protect it.

What About Other Crystals

List of safe Crystals:

  • Crystalline Quartz
  • Amethyst
  • Citrine
  • Rose Quartz
  • Smokey Quartz
  • Granite
  • Microcrystalline Quartz
  • Jasper
  • Agate
  • Sard
  • Jade
  • Petrified wood
  • Onyx
  • Slate (cleaned, can sometimes container fossils)
  • none crystalized Quartz

A list of unsafe rocks and Crystals:

  • Coal
  • Dolomite
  • Limestone
  • Sandstone
  • Pyrite

Unfortunately, these are not a complete list of every rock and crystal available, just the most commonly asked about ones.

If you have something that’s not on this list you wish to add to your aquarium, feel free to leave a comment below. Always do your own research before adding anything to the aquarium.

It’s better to be safe and know what you’re adding than risking the lives of your fish, and the cycle of your tank.


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