Clearing Up Algae

I have a 380-gallon water garden. It has an electric pump, a bell fountain and fish that eat mosquito larvae. My problem is algae.

Water clarifiers are expensive and don't work, and I don't want to resort to toxic, algae-killing chemicals. Any advice to clear up the water?

—Skip Berlin, Eugene, Oregon

Melinda:

Let's start by analyzing your current setup. Is the pump rated to handle this amount of water or more? To keep water clear, it should pump at least half the pond's volume (190 gallons in your case) each hour. If you have more fish than plants, think about installing a pump that circulates that total volume each hour.

Now check the filtration system. Mechanical filters physically remove impurities and should be rated to handle the same volume of water as your pump. If they don't, some of the water may be diverted around the filter and end up unfiltered.

Biological filters trap impurities and support growth of bacteria that help absorb excess nutrients and chemicals that encourage algae growth.

Barley straw is a good example of a natural algae fighter. Anchor it in the pond in an area with moving water at the start of the season. As the straw breaks down, it inhibits the growth of algae.

Don't forget to look at the rest of the pond's ecosystem as well. Be sure to skim off leaves and other plant debris as they land on the pond. Avoid overloading the pond with fish.

There are varying recommendations as to how many fish to add. One common rule is to start with 1 inch of fish for every square foot of pond surface. More than this may put your system out of balance. Keep in mind fish will grow. You may need to increase filtration or adopt out some fish as they multiply and get larger.

Plants should cover about 50 percent of the pond's surface. This helps reduce light, thus limiting the algae population.

If you have made these adjustments and still have problems, you may want to call in an expert. The money spent for professional help may save you lots of time and frustration in the long run.