Does limestone increase algae problems?
A16. In my experience, usually it does, but not always. In water saturated with limestone, the pH will stabilize at around 8.3 favouring some forms of algae over plants. In ponds starved of phosphorus or any other essential nutrient for algae, the limestone will make no difference. Most ponds, however, have an abundance of essential nutrients. Limestone releases calcium into the water. Where limestone increases the algae, calcium may be the nutrient limiting algae growth in the pond. Another factor could be that limestone releases carbon dioxide as plants and algae take it up. Carbon dioxide is used in photosynthesis. I’m told that injection of carbon dioxide into hydroponic water increases production. In time, chemical reactions on the surface of the limestone seal it off from the water. When we clean the pond, however, we scrub the limestone clean once again exposing it to the water. If you have limestone in your pond, wash it off with a gentle spray.
