Should I put rocks in my pond?


Putting rocks or gravel in the bottom of a koi pond is probably one of the most common mistakes new pond builders make. Admittedly, they do look very good at first. Here is the problem with rocks on the bottom of a pond.

  • Rocks prevent fish waste from getting to the bottom drain. Any fish waste that falls to the pond’s bottom will be trapped in the rocks. Now, instead of being swept away into your pond’s filter where it can easily be removed, this waste just sits there creating a sludge on the bottom of your pond. This sludge can degrade your water quality and provide a home for harmful bacteria and parasites. The only way to remove this sludge is to remove and store the koi, drain the pond and vacuum the sludge out of the rocks on the pond’s bottom. This is a huge job.
  • Additionally, rocks will trap leaves and debris on the bottom. Most leaves as they decompose give off tannin acid. Tannin acid will not bother the koi but it will turn the pond water a root beer color. You see this often times with a pond or a stream that has rocks or gravel on it’s bottom. You can perform a 100% water change but within one week the pond water will return to the root beer color again. Just as in the case with the fish waste, the only way to alleviate this problem is to drain the pond or stream and thoroughly wash all the rocks.

You can avoid all these problems by keeping rocks off of the bottom of the pond. Creating a shelf around the sides of the pond extending 12 to 18 inches below the water surface and then installing rocks on this shelf can create a beautiful effect. Once the pond is filled with water, this shelf gives the illusion that the rocks extend all the way to the bottom of the pond. Now, if you keep the pond bottom free of rocks or gravel, you contour the bottom so that the bottom drain is at the lowest point of the pond, and there is a gradual slope leading to it from all sides of the pond, you will have the best of both worlds. You will have a beautiful looking pond while at the same time, a pond that is easier to maintain.