Lakes and Reservoirs


Hydrothol 191 is a liquid formulation that provides control of both weeds and algae. Used primarily as an algicide at rates of 0.05-0.3 ppm, it provides excellent control of a broad spectrum of algae including planktonic, filamentous, and branched algae. Hydrothol 191 also provides control of aquatic vascular plants and can be tank-mixed with Aquathol K to improve the efficacy on difficult-to-control weeds. Hydrothol 191, works relatively quickly providing algae control in just a few days, and weed control similar to Aquathol K. There are no restrictions on treated water used for swimming, fishing or irrigation*.

*Read and follow label directions.


Hydrothol® 191 Facts:

  • Minimal water use restrictions*
  • Controls both weeds and algae
  • Works quickly
Always read and follow label directions. For more information, read labels and other resource material.

Active Ingredients

53.0% Mono(N,N-dimethylalkylamine) salt of endothall
47.0% Other Ingredients
100% Total

*7-oxabicyclo [2.2.1] heptane-2,3-dicarboxylic acid equivalent 23.36%Contains 2 lbs. endothall acid per gallon


Lakes and Reservoirs