Elodea (Elodea canadensis), also known as common water weed, grows in ponds in U.S. Department of Agriculture plant hardiness zones 5 through 9. Depending on how you use your pond, elodea can be a blessing or a curse. While it benefits pond life, when overgrown it can make even the most gorgeous backyard pond look unsightly.
Elodea is an underwater plant that has many branches and thin, dark green, waxy leaves. Unlike many water plants, elodea stays green, even in winter. It may also have waxy, white floating flowers.
If you have a small backyard pond with fish, elodea may benefit the ecosystem. In moderation, elodea serves as a food source and gives fish hiding spots. It also feeds smaller insects and invertebrates that fish may eat. If your pond enjoys visits from small amphibians, elodea or the insects that eat it may attract them.
Dense growth of elodea is usually caused by excessive nutrients from overuse of fertilizers in your own or your neighbors' lawns. If you think fertilizer runoff is reaching your pond, avoid using fertilizer nearby. If your pond contains koi or other fish, too much elodea can reduce available oxygen and potentially kill them. If you think fertilizer is getting into your pond, you can build a barrier to keep runoff out of the pond. If fertilizers still get into the pond, the elodea will continue its fast growth rate.
For small ponds, you can remove elodea by hand by reaching in and pulling up as much of the plants and roots as possible. To remove elodea from a larger pond, use a rake. Drag the rake across the surface of the water until you have pulled out as much as you want to remove. This will not keep elodea at bay permanently and you will have to remove it consistently. You don't need to use chemicals, and the chemicals may kill your fish.