Aquarium Gravel

Be aware that not all gravel is inert. For example, coral, sea shells, dolomite and limestone will release (leach) carbonates into the tank raising its pH buffering capacity. When keeping saltwater fish and corals or African rift lake cichlids, this is desirable. But in most other cases, you will not want your gravel affecting the water chemistry. As a quick test, drip an acid (e.g., vinegar) onto the gravel in question. If it foams or bubbles, the gravel is going to leach carbonates into the water. To be absolutely sure, fill a bucket of gravel with water and measure the pH over a period of a week. If the pH remains stable, it should be safe to use in your tank. If you have obtained non-aquarium gravel for use in your tank, you should test to be sure the gravel does not contain any harmful toxins. Unfortunately, the best way to test the gravel is to add the gravel to a container or small tank, fill with water and add a small fish (preferably a feeder fish) for a few days to be sure the gravel is safe.