FORM OF CONVERTIBLE NOTE

Ex. 4.1

FORM OF CONVERTIBLE NOTE

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE “SECURITIES ACT”) OR APPLICABLE STATE SECURITIES LAWS, AND, ACCORDINGLY, MAY NOT BE OFFERED OR SOLD EXCEPT PURSUANT TO AN EFFECTIVE REGISTRATION STATEMENT FOR SUCH SECURITIES UNDER THE SECURITIES ACT AND APPLICABLE STATE SECURITIES LAWS OR PURSUANT TO AN OPINION OF COUNSEL REASONABLY SATISFACTORY TO THE COMPANY THAT THERE IS AN AVAILABLE EXEMPTION FROM THE REGISTRATION REQUIREMENTS OF THE SECURITIES ACT.

FOR VALUE RECEIVED, BIOLARGO, INC ., a corporation organized under the laws of the state of Delaware (“ Issuer ”), promises to pay to the order of xxxxxx (hereafter, together with any subsequent holder hereof, called “ Holder ”), at its office, at “Holder’s Address” (as that term is defined below), or at such other place as Holder may direct, the “Amount” noted above (the “Loan Amount”), payable on June 1, 2012, or at an earlier date as provided herein (the “ Maturity Date ”). This convertible note is duly authorized issue of the Issuer, issued on the “Date” noted (the “ Issuance Date ”), and designated as its Convertible Note due June 1, 2012 (the “ Note ”).

The Issuer agrees to pay interest on the unpaid principal amount of the Loan Amount from time to time outstanding hereunder at the following rates per year, compounded annually: (i) before maturity of the Loan Amount, whether by acceleration or otherwise, at the rate per annum equal to ten percent (10%); (ii) after the maturity of the Loan Amount, whether by acceleration or otherwise, until paid, at a rate per annum equal to fifteen percent (15%).

Payments of both principal and interest are to be made in immediately available funds in lawful money of the United States of America, or in Common Stock of the Issuer as set forth below.

Accrual of interest shall commence as of the Issuance Date. Interest will accrue monthly and be paid annually on the Note on June 1st (pro-rated based on the actual number of days elapsed in a 365-day year), such interest to be paid, at the Company’s option, in cash or in that number of shares of Common Stock of the Issuer (the “ Common Stock ”) at a price per share equal to the average closing price of the Company’s common stock for the 20 trading days preceding a given interest due date. Unless otherwise agreed in writing by both parties hereto, the interest so payable will be paid to the person in whose name this Note (or one or more predecessor Notes) is registered on the records of the Issuer regarding registration and transfers of the Note (the “ Note Register ”), provided, however, that the Issuer’s obligation to a transferee of this Note arises only if such transfer, sale or other disposition is made in accordance with the terms and conditions contained in this Note and the Subscription Agreement (the “ Agreement ”) that the Holder executed at the time of making an investment in the Issuer.

The Note is subject to the following additional provisions:

1. The Issuer shall be entitled to withhold from all payments of principal and/or interest of this Note any amounts required to be withheld under the applicable provisions of the Internal Revenue Code of 1986, as amended, or other applicable laws at the time of such payments.

2. This Note has been issued subject to investment representations of the original Holder hereof and may be transferred or exchanged only in compliance with the Securities Act and applicable state securities laws and in compliance with the restrictions on transfer provided in the Agreement. Prior to the due presentment for such transfer of this Note, the Issuer and any agent of the Issuer may treat the person in whose name this Note is duly registered in the Note Register as the owner hereof for the purpose of receiving payment as herein provided and all other purposes, whether or not this Note is overdue, and neither the Issuer nor any such agent shall be affected by notice to the contrary. The transferee shall be bound, as the original Holder by the same representations and terms described herein and under the Agreement.

3. The Holder may, at its option, at any time convert the principal amount of this Note or any portion thereof, and any accrued and unpaid interest thereon, into such number of shares of fully paid and non-assessable Common Stock of the Issuer (“ Conversion Shares ”) as is obtained by dividing the Loan Amount by $0.55 (“ Conversion Price ”). The right to convert the Note may be exercised by the Issuer by telecopying, mailing (via first class mail, postage prepaid) or personally delivering an executed and completed notice of conversion (the “ Notice of Voluntary Conversion ”) to the Issuer. The business day (a “ Business Day ”) on which a Notice of Voluntary Conversion is delivered in accordance with the provisions hereof shall be deemed the “ Voluntary Conversion Date ”. The Issuer will transmit the certificates representing Conversion Shares issuable upon such conversion of the Note (together with the certificates representing the Note not so converted) to the Holder via express courier, by electronic transfer (if applicable)