A pond makes a nice addition to the landscape, but many ponds are plagued with pond weeds and other unwanted vegetation. If you have fish in your pond, you may find that you have a blanket weed problem. The blanket weed thrives on the minerals that are found in fish excrement. Many ponds also have a problem with too much algae, and with weeds that grow around the perimeter of the pond. There are several ways to try to control what is growing in your pond using chemicals, aerators and other equipment.
Use pond aerators. Pond aerators can be used to add oxygen to the water, and they release carbon dioxide into the atmosphere. Once the carbon dioxide in the water gets low enough, the plants starve, and the lake weeds die. This is one of the more ecologically friendly ways to get rid of unwanted vegetation, but its usage may depend on what size your pond is and what kind of equipment you can reasonably install in it. If you have other plants that you want to live in your pond, this can also affect them.
Dye the pond water. Pond shade products can dye the water, reducing the sunlight that reaches the pond weeds. They have been shown to be safe for fish, but any plants submerged in your pond will also be affected. These are black dyes that are added to the water.
Add metallic ions like copper that have also been used to kill blanket weeds. If these are not used in the proper amounts, however, they can also kill fish and other animals, so it is important to do your research before using this kind of treatment.
Consider leaving some pond weeds. It may even be desirable to leave some weeds around your pond. Cattails and other naturally occurring vegetation can be an attractive addition around the edges of a pond. If you find the area is starting to be overrun with such plants, however, you should consider removing them.
Try using a tiller or hoe to remove weeds that you can reach. However, many of these plants have roots deep in the ground, so it may be difficult to dig them out completely.