Cyanotech (CYAN) 10-K 2010 FY Annual report

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Exhibit 32.1

Certification Pursuant
To 18 U.S.C. 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, 2010 as filed with the Securities and Exchange Commission on the date hereof (the "Report"), I, David I. Rosenthal, Interim Chief Executive Officer of the Company certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, 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 24, 2010 /s/ David I. Rosenthal
David I. Rosenthal,
Interim President and Chief Executive Officer
and Director
(Performing the Functions of
Principal Executive Officer)

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Exhibit 32.1

Certification Pursuant To 18 U.S.C. 1350, As Adopted Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002