Hydrothol 191 Aquatic Algaecide and Herbicide, manufactured by United Phosphorous, is an excellent algaecide and aquatic herbicide that controls a broad-spectrum of weeds and algae in large water bodies.

By spraying this contact algaecide and herbicide you can achieve a healthier, more attractive lake, pond, and other water sites from weeds like fanwort, algae, and eelgrass. After spraying weeds on the surface of labeled water sites you can see visible results in a couple of days. 

Hydrothol 191 Aquatic Algaecide and Herbicide is a rapid-acting commercial aquatic plant management tool that tackles a wide range of difficult-to-control weeds. 

Tools Needed

To apply Hydrothol 191 Aquatic Algaecide and Herbicide, you will need to use either a backpack sprayer, spray rig, or injection system that can be used underwater. 

How to Use

• Step 1: Measure the size and depth of body of water to determine how much Hydrothol 191 Aquatic Algaecide and Herbicide you will need. To determine acre-feet volume, measure the length, width, and depth of the waterbody, and then divide by 43,560 (length x width x depth / 43,560 = acre-feet). To control algae in quiescent or slow-moving waters, use 0.6-3.6 pints of Hydrothol 191 Aquatic Algaecide and Herbicide per acre foot. For floating algae mats in quiescent or slow-moving waters, apply 0.5 gallons of product per surface acre. To get rid of submerged aquatic plants in quiescent or slow-moving waters, use 1.4-6.8 gallons of product per acre foot. Refer to the label for specific application rates. 
• Step 2: Spray the Hydrothol 191 Aquatic Algaecide and Herbicide on top of the water surface where you see weeds/algae. For injection applications under the water try to move the application tool close to undesired vegetation. If you are making applications above 0.3 ppm then you will need make each treatment as marginal or sectional applications to avoid toxicity to fish. 

Where to Use

Hydrothol 191 Aquatic Algaecide and Herbicide can be used on lakes, ponds, other quiescent water bodies.

Do not use this product in waters containing Koi or hybrid goldfish. 

When to Use

Use Hydrothol 191 Aquatic Algaecide and Herbicide when weeds and algae are actively growing. 

Safety Information 

Hydrothol 191 Aquatic Algaecide and Herbicide is safe to use around children and pets when applied according to the product label instructions. Always wear the proper personal protective equipment (PPE) when mixing and applying this product. 

Special Considerations

Hydrothol 191 Aquatic Algaecide and Herbicide is not intended for use in small volume garden pond systems.