Controlling Springtime Algae Blooms

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Oh, my aching muscles...

By Diahan Krahulek

Ah, springtime! The cold and snow are gone. Birds and animals are coming out of hiding. Flowers are beginning to peek through the ground. And you can’t wait to bring your backyard water oasis back to life!

Creating a beautiful water garden environment to enjoy throughout the summer and autumn is a fun spring project. Unfortunately, one of the most common and frustrating problems for pond keepers is out-of-control algae. With a ”spring cleaning” plan, you will reduce the appearance of the green water or string algae that detracts from the beauty of your pond.

Sunlight and organic matter such as fish waste, leftover food, and decaying leaves provide nourishment to algae “blooms”—when algae erupts in spring. If you reduce exposure to these nutrients, you won’t have to worry about the “green stuff” later in the season.

Here are a few ideas that will give you a solid start for a healthy, well-balanced pond this year:

Spring Cleaning Tips

Perform a 50 percent water change. This process is a very important step in re-starting your pond after the long winter. You will find it much easier to remove debris and sludge and even check fish for injuries or other health issues. Be sure to stir up the water while it’s draining to maximize waste removal. You may want to follow up with a 25 percent water change in a week or so, but don’t do any more until your pond is well-established. This partial change allows you to retain many biological elements that are vital to a healthy pond. Clean out anything that may have fallen in during the winter and brush off rocks and waterfalls before rinsing with a garden hose. Add a water conditioner that removes chlorine and chloramines to the tap water you put back in the pond.

Jump start your pond with “good bacteria.” Available in powder or liquid forms, this bacteria consumes the nitrogen that feeds algae. Add it when you start your pond in the spring and follow up with regular weekly dosages.

Don’t panic when you see algae bloom! It is quite common—and usually expected—to see a small algae bloom in the first two or three weeks after you start your pond. No pond is ever completely free of algae, but, if you’re prepared for it, you will be able to keep it under control without stress.

Preventing Algae Growth

Use the right equipment. Invest in a biological filter and a separate water pump that fit the needs of your pond. You’ve probably heard this before, but it bears repeating: Choose a filter and a pump that are larger than the recommendations printed on equipment packaging. This is especially important if you have Koi or a lot of debris. By filtering pond water efficiently, you will remove elements that feed algae. Your local lawn and garden retailer is an experienced and invaluable troubleshooter in helping you choose the right equipment.

Add “good bacteria” regularly. As mentioned earlier, these products help get your pond up and running quickly, but, with weekly treatments, you can maintain a crystal clear pond. Because the bacteria breaks down toxic ammonia from fish waste and decay into harmless nitrates, you remove nutrition sources from the organic matter to starve algae.

Shade 60 to 70 percent of the pond surface. Reduce direct sunlight to reduce algae growth. Water plants and trees offer the simplest and most natural way to shade your pond. Just be sure that the trees aren’t so close to the pond that they add more debris. Sun-blocking dyes also help reduce sunlight exposure but are not recommended for heavily planted ponds since they also hinder photosynthesis.

Add plants. Surface plants like water lilies, hyacinths, and lotus reduce direct sunlight to your pond. Submerged plants, such as anacharis and cabomba, add oxygen and absorb nutrients from fish by-products to take away algae food sources.

Don’t overfeed or overstock your fish. You’ve heard the old adage “garbage in, garbage out.” It rings true for feeding your fish, too. Feed high-quality floating Koi food using the recommended amounts on the packaging. In this way, you reduce the amount of waste the fish produce and eliminate leftover food that will sink to the bottom. Do not overfeed your fish—even if they beg! Until the biological filtration in your pond is established, add only a few small fish. You can introduce more later using the standard formula of one inch of fish per square foot of pond surface.

Schedule regular cleanings. If you spend a little time each week removing debris and sludge, you will avoid bigger problems later in the season. Check your filter and pump weekly to prevent clogging, and add a weekly treatment of a beneficial bacteria product. Plan a 25 percent water change once a month to make sure that normal sludge in the pond is never more than one-forth of an inch high.

If Algae Becomes a Problem

Regardless of your best intentions, you may experience some algae issues. There are several things you can do to address new growth:

Add an algaecide. Algaecides are good quick fixes if you follow manufacturer instructions. Do not use them, however, as ongoing preventatives as they may prevent your pond from establishing its own balanced system.

Immediately reduce fish food amounts. Whether the fish eat it or let it drop to the bottom, adding food increases nutrients for algae. Temporarily cut back on the amount you use.

Install an ultraviolet clarifier. Ultraviolet light eliminates green water by destroying single-cell algae. Buying a UV clarifier can be expensive, but it’s a great investment for a long-term solution. Read the manufacturer’s directions carefully to ensure the clarifier is placed, installed, and handled properly, and don’t forget to change the UV bulb every spring.

The main thing to remember is don’t panic! With a plan of action, you can spend more time enjoying your pond and less time fighting with algae this year.  NWGN


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