Question
what type of gravel is found in a pond???what are the other types of soil that are found in a pond???

Answer
Hi,
depending on the type of pond some have gravel in and some soil but they both must be free from pollutants and fertilizers, but if you keep koi you have neither soil, gravel or plants in your pond.
you can visit my pond at http://koi-z-are-us.20m.com
George.