Exhibit 32.1

Certification of CEO and CFO

Pursuant to 18 U.S.C. Section 1350,

As Adopted Pursuant to Section 906

of the Sarbanes-Oxley Act of 2002

In connection with the Annual Report of Cyanotech Corporation (the “Company”) on Form 10-K for the period ended March 31, 2023 (the “Report”) as filed with the Securities and Exchange Commission on the date hereof, each of the undersigned certifies that:

1) The Report fully complies with the requirements of Section 13(a) or 15(d) of the Securities Exchange Act (15 U.S.C. 78m or 78o (d)); and

2) The information contained in the Report fairly presents, in all material aspects, the financial condition and results of operations of the Company.

Date: June 27, 2023	/s/ Matthew K. Custer
	Matthew K. Custer
	President and Chief Executive Officer
Date: June 27, 2023	/s/ Felicia Ladin
	Felicia Ladin
	Chief Financial Officer; Vice President—Finance & Administration, and Treasurer
	(Principal Financial Officer)