Hydrothol Granular Aquatic Algaecide & Herbicide
Control pond algae and submerged aquatic weeds with Hydrothol Granular 20 lb, an endothall-based algaecide for lakes, ponds, canals and shoreline treatments.
Hydrothol Granular 20 lb is a professional-strength aquatic algaecide and herbicide designed to control nuisance algae and selected submerged aquatic weeds in ponds, lakes, drainage canals and other quiescent, slow-moving or flowing aquatic sites. Its active ingredient is 11.2% mono(N,N-dimethylalkylamine) salt of endothall, equivalent to 5% endothall acid, and the product is registered under EPA Reg. No. 70506-174.
Built for fast, targeted control, Hydrothol Granular is commonly used for pond algae control, lake weed control, shoreline treatments, dock areas, swim-access lanes, irrigation paths and drainage systems where the product is registered and label directions allow use. UPL describes Hydrothol Granular as a product that controls both weeds and algae, works quickly, and is primarily used at 0.05–0.3 ppm for broad-spectrum algae control, including planktonic, filamentous and branched algae.
Hydrothol Granular is especially useful when algae or weeds are actively growing. It can help manage problem species such as chara, filamentous algae, coontail, hydrilla, milfoil, naiad, elodea, pondweeds and water stargrass, depending on label-permitted use, treatment rate, water conditions and local regulations. The label notes that algae susceptibility may vary by subspecies, strain and environmental conditions, so accurate plant identification and proper rate selection are important.
Algae blooms are more than a cosmetic issue. EPA explains that excessive algae growth can consume oxygen, block sunlight and make aquatic life survival difficult when algae die and decompose; WHOI also notes that many fish kills are linked to low-oxygen or no-oxygen conditions created by blooms.
Key Benefits
| Benefit |
Why It Matters |
| Controls algae and aquatic weeds |
Targets planktonic, filamentous and branched algae, plus many submerged weed species. |
| Granular contact formula |
Easy to distribute over shoreline, spot and marginal treatment areas. |
| Works in still and moving water |
Labeled for quiescent, slow-moving and flowing aquatic sites. |
| Useful for targeted access areas |
Helps clear dock, shoreline, swim-lane, irrigation and drainage access zones when used according to the label. |
| Endothall-based chemistry |
EPA’s archived technical fact sheet reports that endothall is not expected to adsorb strongly to suspended solids or sediments in water and is not expected to bioaccumulate in aquatic organisms.
|
Best Uses
| Application Area |
Common Targets |
| Ponds and small lakes |
Filamentous algae, chara, coontail, milfoil, hydrilla, naiads, pondweeds |
| Lake shorelines and docks |
Submerged weeds and bottom-growing algae around access areas |
| Drainage canals |
Algae mats and aquatic vegetation that restrict water movement |
| Irrigation systems |
Labeled aquatic weed and algae control where permitted |
| Spot and sectional treatments |
Marginal areas, boat lanes and limited-use zones |
Label-Based Application Rate Summary
Always follow the current product label. Rates vary by target species, water depth, infestation level, water movement, and treatment objective.
| Treatment Target |
Endothall Acid Rate |
Hydrothol Granular Rate |
Notes |
| Light to moderate planktonic or filamentous algae |
0.05–0.3 ppm |
3–16 lb per acre-foot |
Repeat only when algae reappear and reach treatment levels. |
| Branched algae / difficult algae |
Up to 3.0 ppm |
Up to 162 lb per acre-foot |
Applications above 0.3 ppm are suggested for commercial applicators as marginal or sectional treatments due to fish-toxicity concerns. |
| Submerged aquatic plants |
0.5–5.0 ppm |
27–270 lb per acre-foot |
Professional application is recommended, especially for larger or higher-rate treatments. |
| Ponds/small lakes with little to no outflow — planktonic & filamentous algae |
0.25 ppm |
15 lb per acre-foot |
Label example for small lakes/ponds. |
| Ponds/small lakes with little to no outflow — branched algae & aquatic plants |
0.5 ppm |
30 lb per acre-foot |
Label example for small lakes/ponds. |
Quick Rate Chart
| Rate |
Pounds per Acre-Foot |
Ounces per 1,000 sq. ft. per Foot of Depth |
| 0.05 ppm |
3 lb |
1.0 oz |
| 0.1 ppm |
5 lb |
1.9 oz |
| 0.3 ppm |
16 lb |
5.8 oz |
| 0.5 ppm |
27 lb |
10 oz |
| 1.0 ppm |
54 lb |
20 oz |
| 2.0 ppm |
108 lb |
40 oz |
| 3.0 ppm |
162 lb |
60 oz |
| 5.0 ppm |
270 lb |
100 oz |
Important Safety & Use Restrictions
| Topic |
Label-Based Guidance |
| Read the label first |
It is a violation of federal law to use this product in a manner inconsistent with its labeling. |
| Fish and aquatic life |
The label states this pesticide is highly toxic to fish and aquatic invertebrates, and fish may be killed by dosages above 0.3 ppm. Dense algae or plant growth should be treated in sections to reduce oxygen-loss risk from decomposing vegetation. |
| Professional application |
For higher-rate algae applications and submerged plant control, commercial applicators are recommended for marginal or sectional treatments. |
| Do not use in certain ponds |
Do not use in waters containing Koi or hybrid goldfish. The product is not intended for small-volume garden pond systems. |
| Water type |
Do not use in brackish or salt water. |
| Potable water |
Consult state or local water authorities before applying to public waters. The label includes a 600-foot setback from functioning potable-water intakes in lakes, ponds and other quiescent water bodies. |
| Treatment size |
Do not treat more than 10% of the area at one time with doses above 1 ppm. |
| PPE |
Mixers, loaders, applicators and handlers must wear label-required protective clothing, gloves, protective eyewear and approved respiratory protection unless a label exception applies. |
Shipping Restrictions
| Restricted Shipping States for This Listing |
| CA, CT, NJ, NY, WA, OR, ME |
