Safety

• Polished river rock is a safe addition to an aquarium. It is a non-porous rock, so it does not absorb algae and sediment; hence, it is easy to clean. If properly prepared and cleaned---before being placed into the aquarium---it is safe for fish.
  
  

Use

• Polished river rock should be used only as decorative accent, not as the substrate in an aquarium. Small size pea gravel should form the bottom layer of the aquarium, to help in filtering the water and keeping the aquarium clean.
  
  

Warning

• If you buy polished river rock for aquarium use, be sure it is actually polished rock and not painted glass. Some polished river rocks are made from glass, and painted to look like rocks. The paint will eventually flake off in the aquarium, and your fish might eat the paint flakes, thinking they are food flakes. These painted rocks also may contain toxic ingredients, which could poison the water. Boil rocks for ten minutes prior to placing them in the tank. Boiling ensures that any bacteria has been killed and that the rocks are real and not painted.