Hydrothol 191 is a monoamine salt; in what algae context is it used?

• A. Hydrothol 191 is a monoamide salt used on some algae
• B. Hydrothol 191 is a dipotassium salt used for submerged plants
• C. Hydrothol 191 is only effective against moss
• D. Hydrothol 191 is not used for algae

Answer: (A)

Hydrothol 191 is the monoamide salt form of endothall, and this formulation is used specifically as an algaecide for certain algae in aquatic settings. It works as a contact kill, affecting algae that come into direct contact with it in the water. This is why it’s described as a monoamide salt used on some algae. The dipotassium salt form would be a different endothall salt and isn’t what Hydrothol 191 represents, and Hydrothol 191 is not intended for submerged aquatic plants or moss.