Can I Use Outdoor Gravel in My Aquarium?

Question: Can I Use Outdoor Gravel in My Aquarium?

Answer: Maybe, hows that for a definitive answer?

Mixed Feelings
Experts and fish enthusiasts alike are divided on this subject, so don't be surprised if you see opposing answers to this question. The reason is that certain materials can cause a change in the pH and hardness of your aquarium water, which can be harmful to your fish. Some people feel comfortable advising only using rocks and substrates purchased from a pet shop. Others will describe how to test rocks and gravel to rule out hazardous materials.

I'm one of those who believe using outdoor rocks and gravel is great - but only if you are willing to test them. If you don't intend to test your rocks and gravel, purchase them from a pet shop. Be aware that on occasion even materials sold in pet shops have been known to be hazardous.

How to Test
Testing can be as simple as placing a few drops of vinegar on the rock or gravel you are considering using. If it fizzes or foams, don't use it, as it contains calcium deposits. Another way of testing rocks and gravel is to place them in a bucket of the same water that you use in your aquarium. Test the pH and hardness, and then let it sit for a week and test again. If there is a significant change, the rocks or gravel are likely to cause problems.

What Can Be Used
What to avoid are rocks that are highly calcareous – meaning they have a large amount of calcium. Calcareous rocks and gravel will alter the hardness and pH of your water.
Rocks to Avoid include:

• Limestone
  
• Marble
  
• Geodes
  
• Dolomite
  
• Shells or crushed coral
  
  

Safer Rocks Include:

• Granite
• Quartz
  
• Slate
  
• Lava Rock
  
• Onyx
  
• Sandstone (should always test before using)
  
  

Regardless of the type of rock or gravel, you should test it to be sure. Take care to choose rocks that have smooth edges, as sharp edged rocks can harm your fish.

Where to Get It
Rocks and gravel can be procured from:

• Outdoors – avoid riverbeds, as you can disturb the native habitat
  
• Garden nurseries
  
• Gardening centers at department stores
  
• Landscaping companies
  
  

All of these sources can provide you with inexpensive and attractive rocks and gravel. Just remember to take care in making your selections, and always test before you using it in the aquarium. Happy rock collecting!