Which Aquarium Rocks Are Harmful To Your Fish Tank?

Aquarium rocks are for mostly to dress up your fish tank.   While aquarium caves and rocks are great decorations, they have another function as well.  They provide the perfect shelter for your fish to hide under.  As with anything you put in your tank there are some things to take note of before picking out your aquarium rocks.  You want to choose rocks that are inert, and do not affect the chemical balance of your tank.   Because of this, it’s best to avoid putting rocks in your tank that you just find outside.  Rocks purchased from aquarium retailers should be well labeled so you know what you are getting.  Take a look at the list below to help you as well.

Aquarium Rocks to Avoid

• Pyrite
• Galena
• Marble
• Limestone
• Chalk
• Dolomite
• Geodes

Aquarium Rocks That Are Suitable For Freshwater Aquariums

• Artificial Rocks
• Granite
• Onyx
• Quartz
• Slate
• Sandstone
• Flint
• Lava Rock

Can I Test Rocks I Find?

If you want to be certain of the effects before introducing new rocks to your tank you could always test them first.  Just put your rocks in a water bucket and test the pH level.  Leave the rock(s) in the bucket and after a week test the pH level again.  If there is a change in the pH level, you might reconsider adding the rocks to your tank.

Watch For Sharp Edges

Lastly, you’ll want to make sure your aquarium rocks do not have jagged or sharp edges.  Your fish can hurt themselves on these types of fish tank rocks.  Smooth or rounded rocks are suggested.

What kind of rocks do you have in your tank?