Get ahead of the growth

Aquatic dyes not only give a pond a consistent color, but they can block some aquatic weeds and algae from getting a quick start at the beginning of the season. Rob Richardson, associate professor and extension specialist at North Carolina State University, shares some of the top tips for effective application.

How do aquatic dyes stop weeds and algae from developing?

The purpose of a colorant is to block sunlight and prevent it from reaching weeds and algae, so their photosynthesis is impacted. It’s important to get it out and start with your colorant early in the season before the problems manifest. If you’re targeting a submersed plant, a plant that grows from the bottom of the pond toward the surface, you need to get the colorant out before that plant grows up to the upper 24 inches of the water column or it’ll have enough sunlight in there to become weedy. For some plants, like duckweed and watermeal, the small floating plants, it might be possible to slow those plants down or prevent them from coming back up to the surface because they sink to the bottom in the winter. If you’re trying to get rid of those, you have to get your color out really early, depending on where you are in the country, get it out before those plants pop up to the surface.

It’s the same with various types of algae that you might be trying to reduce or stop. Some of them start at the bottom and float to the top, but others start at the surface. Either way, you really need to get your colorant out before those problems manifest themselves. And you want to keep a concentration of colorant in place through the growing season so they don’t have a chance to start conducting photosynthesis and become weedy.

How early do you mean?

Not early as ice on the water. But it needs to be out before these problems would typically show up. So let’s say you have a weed, and you usually see that weed in mid April. You probably want to have your colorant established by mid-March. It needs to be correlated to the life cycle of the specific weed and you need to have it out before that target pest shows up.

Does the concentration of the colorant make a difference?

These are all essentially dyes, so the pigment just absorbs whatever spectrum of sunlight it can. So the darker it is, the more of the spectrum it’ll be absorbing. It can help with algae; even things like phytoplankton are going to be impacted. We usually don’t recommend that dyes are going to be used in ponds where you want to raise trophy bass or big fish for a fishery, because you’re going to reduce the phytoplankton bloom, which is going to reduce the zooplankton bloom, which means less food for small fish which is less food for big fish.

There’s not been a lot of research as to whether the color makes a difference. The biggest difference I can think of is some of these products are registered for weed control and some are just registered for pond coloring or water clarity or whatever. You have to be careful that you’re using these products consistently with either how they’re labeled.

You can use the pond dyes in combination with just about any other control measure. They may reduce effectiveness of some of the herbicides, some of the ones that need sunlight in order to impact the plants. But by and large they can be used with any other control measure. I wouldn’t recommend using it just a single time unless there’s something down in the water that can be covered up by reducing how far people can see down into the water. You can’t just put these out in the middle of the summer and expect them to control or reduce weed growth at that point. If you really want to use these for weed or algae growth you need to get them out early in the season and you need to maintain that concentration of dye for that water color throughout the season.