Hydrothol 191 Aquatic Algaecide & Herbicide, 2.5 Gallon
Hydrothol 191 Aquatic Algaecide & Herbicide, 2.5 Gallon
$24688
Clear algae and reclaim usable water faster with Hydrothol 191, a liquid aquatic algaecide and herbicide for ponds, lakes, canals, and other labeled water sites. This endothall concentrate is used primarily for algae control at low ppm rates, works quickly on labeled algae, and also treats many submerged weeds.
- Quick visual response; algae results are usually seen in a few days
- Mixed problem fit; controls both algae and many aquatic weeds
- Flexible rate range; supports light algae work or tougher cleanup programs
- Wide site utility; fits ponds, lakes, reservoirs, and canals
- Clear use guidance; label addresses potable-water and fish-toxicity planning
- Professional confidence; EPA-registered with detailed directions and rates
Choose Hydrothol 191 for one liquid treatment that handles more than algae alone.
Always follow label directions.
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Product Description
Control algae and submerged weeds with one liquid program
Hydrothol 191 is built for buyers who need more than an algae-only product. It gives you a flexible liquid option for lakes, ponds, reservoirs, canals, and other labeled sites where algae and submerged weeds can appear together. Because rates are measured in ppm endothall acid and acre-feet, it helps you plan treatment intensity and exposure time with more precision.
Key Features & Benefits
| Feature | Benefit |
|---|---|
| Controls algae and weeds | One liquid treatment can address mixed infestations without splitting the job across multiple products. |
| Low-ppm algae use rates | Helps you match algae treatments to site conditions without defaulting to heavy applications. |
| Surface, injected, drip, or metering use | Fits more equipment and treatment styles in still, slow-moving, and flowing water. |
| Broad target list | Covers planktonic, filamentous, and branched algae plus many labeled submerged aquatic plants. |
| EPA label tables | Gives applicators clear rate structures for acre-foot, surface-acre, ppm, and exposure-time planning. |
Directions & Dosing Snapshot
| Use Case | Label Rate | Application Notes |
|---|---|---|
| Algae in quiescent or slow-moving water | 0.05-0.3 ppm, typically 0.6-3.6 pints per acre-foot | Repeat when algae reappear and reach treatment levels. |
| Tough algae or longer control in quiescent or slow-moving water | 0.3-3.0 ppm, up to 36 pints per acre-foot | Above 0.3 ppm is suggested only as marginal or sectional treatment because of fish-toxicity concerns. |
| Floating algae mats | 3-5% spray solution; minimum 0.5 gallon per surface acre | Coverage is critical. Only sprayed algae are controlled, and results are usually seen in a few days. |
| Submerged aquatic plants in quiescent or slow-moving water | 1-5 ppm, or 1.4-6.8 gallons per acre-foot | Rates above 1.0 ppm are for very narrow margins or areas where some fish kill is not objectionable. |
| Algae in flowing water | 0.05-3.0 ppm for 6-120 hours | Do not exceed 30 ppm per growing season, 5 ppm per application, or 5 ppm in a 7-day interval. |
| Aquatic plants in flowing water | 0.2-5 ppm for 6-120 hours | Use the label formula based on CFS, treatment hours, and ppm to calculate gallons needed. |
Always follow the full label for complete directions, restrictions, and site-specific requirements.
Comparison Table
| Hydrothol 191 | Liquid dipotassium endothall herbicide | Chelated copper liquid algaecide | Biological pond-treatment program | |
|---|---|---|---|---|
| Primary role | Algae plus many submerged weeds | Primarily submerged weed control | Primarily algae control | Organic-load and maintenance support |
| Mechanism | Endothall amine salt, contact algaecide/herbicide | Endothall dipotassium salt, contact herbicide | Copper-based contact algaecide | Beneficial microbes and enzymes |
| Speed cue | Algae often in a few days | Varies by label | Varies by chemistry and algae type | Gradual program effect |
| Best fit | Mixed algae and submerged weed pressure | Weed-focused water treatments | Algae-only cleanup programs | Longer-term pond maintenance |
| Water-use context | Minimal overall restrictions; see potable-water and NY note | Varies by label | Varies by label and water chemistry | Varies by product |
Why Choose a liquid contact algaecide and herbicide?
- Faster cleanup: A liquid contact treatment is a strong fit when access, appearance, or flow conditions call for a quicker response.
- More versatility: Hydrothol 191 can cover algae and many submerged weeds in the same treatment plan.
- Better planning control: Ppm-based rates and acre-foot guidance make it easier to match the treatment to the site.
This product is distributed by NewTechBio as an authorized reseller. Specifications, treatment rates, and performance claims are sourced from the official EPA-approved manufacturer label and published documentation. NewTechBio does not independently verify manufacturer claims. Always read and follow the label.
Last updated for listing accuracy: 04/29/2026
What is Hydrothol 191 used for?
Is Hydrothol 191 the right choice if I have both algae and submerged weeds?
How fast does Hydrothol 191 work, and why does algae sometimes come back?
How much Hydrothol 191 do I need?
How is Hydrothol 191 applied?
Can I use Hydrothol 191 in irrigation canals?
What water-use or fish-related restrictions matter most before I order?
Can Hydrothol 191 be used in koi ponds or small decorative ponds?
What kinds of algae and weeds does Hydrothol 191 target?
Products related to this item
Product Details
Important Information
SDS: View Safety Data Sheet (PDF)
LABEL (Directions & Rates): View Product Label (PDF)
Comments/Other: Review the Product Label and SDS for directions, rates, and safety information.
Certifications / Registrations: EPA registered
Origin: Locally Manufactured, Made in the USA
Feature: Liquid concentrate formulation, Multiple application methods supported
Product Form: Liquid
Product Details
Control algae and submerged weeds with one liquid program
Hydrothol 191 is built for buyers who need more than an algae-only product. It gives you a flexible liquid option for lakes, ponds, reservoirs, canals, and other labeled sites where algae and submerged weeds can appear together. Because rates are measured in ppm endothall acid and acre-feet, it helps you plan treatment intensity and exposure time with more precision.
Key Features & Benefits
| Feature | Benefit |
|---|---|
| Controls algae and weeds | One liquid treatment can address mixed infestations without splitting the job across multiple products. |
| Low-ppm algae use rates | Helps you match algae treatments to site conditions without defaulting to heavy applications. |
| Surface, injected, drip, or metering use | Fits more equipment and treatment styles in still, slow-moving, and flowing water. |
| Broad target list | Covers planktonic, filamentous, and branched algae plus many labeled submerged aquatic plants. |
| EPA label tables | Gives applicators clear rate structures for acre-foot, surface-acre, ppm, and exposure-time planning. |
Directions & Dosing Snapshot
| Use Case | Label Rate | Application Notes |
|---|---|---|
| Algae in quiescent or slow-moving water | 0.05-0.3 ppm, typically 0.6-3.6 pints per acre-foot | Repeat when algae reappear and reach treatment levels. |
| Tough algae or longer control in quiescent or slow-moving water | 0.3-3.0 ppm, up to 36 pints per acre-foot | Above 0.3 ppm is suggested only as marginal or sectional treatment because of fish-toxicity concerns. |
| Floating algae mats | 3-5% spray solution; minimum 0.5 gallon per surface acre | Coverage is critical. Only sprayed algae are controlled, and results are usually seen in a few days. |
| Submerged aquatic plants in quiescent or slow-moving water | 1-5 ppm, or 1.4-6.8 gallons per acre-foot | Rates above 1.0 ppm are for very narrow margins or areas where some fish kill is not objectionable. |
| Algae in flowing water | 0.05-3.0 ppm for 6-120 hours | Do not exceed 30 ppm per growing season, 5 ppm per application, or 5 ppm in a 7-day interval. |
| Aquatic plants in flowing water | 0.2-5 ppm for 6-120 hours | Use the label formula based on CFS, treatment hours, and ppm to calculate gallons needed. |
Always follow the full label for complete directions, restrictions, and site-specific requirements.
Comparison Table
| Hydrothol 191 | Liquid dipotassium endothall herbicide | Chelated copper liquid algaecide | Biological pond-treatment program | |
|---|---|---|---|---|
| Primary role | Algae plus many submerged weeds | Primarily submerged weed control | Primarily algae control | Organic-load and maintenance support |
| Mechanism | Endothall amine salt, contact algaecide/herbicide | Endothall dipotassium salt, contact herbicide | Copper-based contact algaecide | Beneficial microbes and enzymes |
| Speed cue | Algae often in a few days | Varies by label | Varies by chemistry and algae type | Gradual program effect |
| Best fit | Mixed algae and submerged weed pressure | Weed-focused water treatments | Algae-only cleanup programs | Longer-term pond maintenance |
| Water-use context | Minimal overall restrictions; see potable-water and NY note | Varies by label | Varies by label and water chemistry | Varies by product |
Why Choose a liquid contact algaecide and herbicide?
- Faster cleanup: A liquid contact treatment is a strong fit when access, appearance, or flow conditions call for a quicker response.
- More versatility: Hydrothol 191 can cover algae and many submerged weeds in the same treatment plan.
- Better planning control: Ppm-based rates and acre-foot guidance make it easier to match the treatment to the site.
SDS: View Safety Data Sheet (PDF)
LABEL (Directions & Rates): View Product Label (PDF)
Comments/Other: Review the Product Label and SDS for directions, rates, and safety information.
Certifications / Registrations: EPA registered
Origin: Locally Manufactured, Made in the USA
Feature: Liquid concentrate formulation, Multiple application methods supported
Product Form: Liquid
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Reviews
Verified Purchase
It worked. Needed 2 application for shore weeds.
Verified Purchase
Works well no weeds at the lake so far this year.
Verified Purchase
My neighbor used it and it works well for my small pond weeds issue.
Verified Purchase
I mixed and then sprayed thick weeds around my boat house. 80% gone so far. Good product.
Verified Purchase
I tried it on Lake Willow weed and it had no effect. It did kill most other unidentified weeds though, which is good.
