It’s tempting to simply add ‘ology’ to the end of a word when referring to the study of a subject. For that reason many people often refer to a person who studies algae as an algologist. The true meaning of algologist is ‘one who studies pain’. From the Latin root word algos meaning pain.
The correct term for the study of algae is phycology, from the Latin root phycos meaning seaweed. The use of the term algology, as the study of algae, is so prevalent that most dictionaries will define it as ‘the study of algae: see phycology’. To make matters worse I have seen algology defined simply as phycology.
Be warned, when using the correct terms phycology or phycologist, be prepared for people and computers to correct you with, “Do you mean psychology?”