Every ponder has horror stories about algae.

Despite all the bad press, algae does have some redeeming value. It absorbs toxins that would otherwise have adverse effects on pond life and when controlled it serves as a food source when the fish get hungry thus preserving your preferred plants from being nibbled on. In fact, we owe our existence to algae, for it was one of the first forms of plant life on our planet and was a precursor to life as we know it today.

Still, it's hard to be all that thankful when you are out filling a bucket up every day with algae. The key to algae control is simple, though not often easy to achieve. The key also lies in proper balance.
Algae needs 3 things to survive: Water, sunlight and nutrients. The more you control these elements, the less algae you will have. If you have too much algae, then you may have too many fish, making nutrients, or too much sun. Get rid of some fish, beef up your filtration system, and plant more plants that help shade your pond, like water lilies.
There are many treatments that help eliminate algae but they aren't a very good fix in the long run, because you have to keep applying them. The best cure is to do the above fixes, and don't let algae control you! Once you've done what you can, get a tennis racket or a skimmer and just consider algae as part of the package. Algae has been around for eons. It's the morning glory of ponding!

The most common form of algae, and the kind most ponder's despise, is string algae, or bubble algae, which looks like green string-like cotton candy and attaches itself to rocks and sides of ponds. (See Picture)

This type of algae will be present no matter how much work you do to rid your pond of it. It can grow several feet long and in an unbalanced pond, it can grow quickly - up to 5 inches each day. This type of algae will bloom (increased growth) when ever a pond is cleaned and in the spring as the water heats up. The bloom usually lasts for a couple of weeks before calming down provided the pond has a balanced ecosystem.

Removing algae is simple, but only partial, requiring you to use your hands and grab and pull or use a brush. Be care with a brush on pond liner as you may damage it and cause a leak. Tennis rackets work great in smaller ponds. You may use non-iodized salt (not regular salt, it will kill plants and fish) to kill the algae. But this is also a temporary fix. Sprinkle the algae with the salt - it works best if there is no water contact with the algae. Be careful around other plants as they may not be tolerant of the salt either. If you don't have plants or fish, as in a small water feature, you may use handfuls of salt to keep the water clear.

See also Green Water