Summer is here and everything in your pond is in full rhythm, flowers are blooming, and your fish are active. Algae is growing and you’re wondering what do I do about that green water or what is that fuzzy green stuff on my pots and around the sides of my pond. You might even have long, green, stringy algae. Let’s cover some of the basics. Green water is caused by an exploding population of free-floating, single-celled algae. This is the first step in a natural process that establishes a healthy, balanced ecosystem. This should clear up naturally within 4 – 6 weeks as the plants starts to take over. Your pond has to build up beneficial bacteria. You can also add this bacteria yourself to help speed up the process. My pond is clear but I do have fuzzy algae. I have the short, mossy algae that looks like fuzzy hair to me. This grows on my rocks and on my pots. This is good. This is what I want and need to have a well balanced pond. This tells me that the wastes in my pond are properly being broken down and nitrates are being made. This fuzzy algae is working like submergible plants. This keeps my pond clear by removing excess nutrients from the water preventing the pea-soup algae that turns your pond green. Some people like to scrub this off their rocks or pots. They hate algae of any kind. I try to work with Mother Nature not against her. This fuzzy algae also gives my koi something to eat when I’m not around to feed them. DO NOT DRAIN YOUR POND. Mother Nature takes her time to work. If you drain your pond you will have to start all over again. Leave the fuzzy stuff.
Now the stringy stuff. If I could find a way to market this, I would be rich. I had this hanging off my waterfalls. Now that my water hyacinths have grown and cover the top of my falls, they take out the nutrients from my water before they get into my pond. Before this, I had to remove the algae with a bottle or toilet brush. I just twirl the brush around the algae and it removes this offensive plant. Algae is a living plant. It needs sunlight to grow. Keeping your water cover 60% to 65% with plants will help shade your pond or you can use a water dye. Using a dye during the winter will darken your water and keep the winter and early spring sun from giving you an early growth of algae. The dye will dissipate by spring. There is a product produced by Interpet in England that is available in the US known as Pond Balance. The pink crystals are dissolved in water and added to the pond in the early spring. This and other products can be purchased but most only work in the spring when water temperature is below 55°. If you don’t like to remove this string algae you can use a UV sterilizer to kill it. A UV Sterilizer uses ultraviolet light to kill algae and fish pathogens that are free-floating in the water. Koi enthusiasts, who always want clear water, routinely combine a UV sterilizer with biological filtration. Keep the string algae from wrapping around tender young plants, they can strangle and kill plants. Heavy concentration can also suffocate plants or deprive them of necessary sunlight.
Summer is the time to keep your strainers and skimmers clean. Keep adding fresh water to your pond because the hotter weather will cause water to evaporate. Monitor all pond life carefully for diseases and parasites. Treat as needed. Feed your fish at least twice a day. Only feed them as much as they can eat in 5 minutes. It is best to under feed than over feed them. Give them different foods like, lettuce, watermelon, grapefruit, and anything else that they might like. I know of one woman who had her koi for 15 years. One of her koi likes to eat her homemade sausages and another one likes toast with strawberry jam. She also feeds them a variety of fruits and vegetables. Her koi are over 24 inches long.. If you buy new fish, quarantine them for at least 21 days before you release them into your pond with other fish. Quarantine new plants for 14 days before you add them. They could have been kept in a pond with diseased fish and still be harboring disease agents. A final rinse under the tap should prevent anything still attached to them from getting into your pond. Continue fertilizing your plants through August. Run your pump continuously. Aquatic plants add oxygen during the day but remove it from the water at night. Don’t feed your fish if the temperatures goes over 85°. If the water stays over 85° for several days, you may want to add fresh water to cool it down. Do not do more than 25% exchange. Do not have an overstocked pond. Too many fish means too little oxygen.
Darlene Jennings (pond Lady) President, Mid-Michigan Pond & Water Garden Club Advanced MSU Master Gardener