<PAGE>

                                                                   EXHIBIT 10.15


                                   OurPet's

                                    Company


                                PROMISSORY NOTE
                                ---------------


$25,000.00 (Minimum of $25,000)                             Date: August 1, 2000

For value received, the undersigned, OurPet's Company, (the "Borrower"), at 1300
East Street, Fairport Harbor, Ohio, 44077, promises to pay to the order of
Joseph T. Aveni, (the "Lender"), at 6000 Rockside Woods Blvd, Suite 220,
Cleveland, OH 44131 (or at such other place as the Lender may designate in
writing) the sum of $25,000.00 with interest from August 1, 2000, on the unpaid
principal at the rate of 10.00% per annum.

In addition, the Lender shall receive one (1) three-year warrant exercisable at
$1.25/share for each $1.00 loaned. The effective date of these warrants will be
August 1, 2000.

The principal shall be payable in full in one installment of $25,000.00, on July
31/st/, 2002, the Due Date. Interest will be payable quarterly.

All payments on this Note shall be applied first in payment of accrued interest
and any remainder in payment of principal.

If the installment is not paid, in full, when due, the remaining unpaid balance
and accrued interest shall become due immediately at the option of the Lender.

The Borrower reserves the right to prepay this Note (in whole or in part) prior
to the due date with no prepayment penalty.

If the payment obligation under this Note is not paid when due, the Borrower
promises to pay all costs of collection, including reasonable attorney fees,
whether or not a lawsuit is commenced as part of the  collection process.
<PAGE>

If any of the following events of default occur, this Note and any other
obligations of the Borrower to the Lender, shall become due immediately, without
demand or notice:

1)   the failure of the Borrower to pay the principal and any accrued interest
     in full on or before the Due Date;

2)   the filing of bankruptcy proceedings involving the Borrower as a Debtor;

3)   the application for appointment of a receiver for the Borrower;

4)   the making of a general assignment for the benefit of the Borrower's
     creditors;

5)   the insolvency of the Borrower;

6)   the misrepresentation by the Borrower to the Lender for the purpose of
     obtaining or extending credit.

The Lender understands that the promissory note described herein is a
subordinate debt position to other existing senior debt holders or their
successors of OurPet's Company obligations. Currently, these lenders are limited
to The Summit Business Capital Corporation, and the Small Business
Administration.

If any one or more of the provisions of this Note are determined to be
unenforceable, in whole or in part, for any reason, the remaining provisions
shall remain fully operative.

All payments of the principal and interest on this Note shall be paid in the
legal currency of the United States. Borrower waives presentment for payment,
protest, and notice of protest and nonpayment of this Note.

The Company shall not effect any such consolidation or merger unless prior to or
simultaneously with the consummation thereof the survivor or successor
corporation resulting from such consolidation or merger shall assume by written
instrument delivered to the Lender all obligations present and due under the
terms of the Note.

No renewal or extension of this Note, delay in enforcing any right of the Lender
under this Note, or assignment by Lender of this Note shall affect the liability
of the Borrower. All rights of the Lender under this Note are cumulative and may
be exercised concurrently or consecutively at the Lender's option.

This Note shall be construed in accordance with the laws of the State of Ohio.

Signed this 1st day of August, 2000, at Fairport Harbor, Ohio.

Borrower:
OurPets Company

By: /s/ Steven Tsengas
    -------------------------------
    Steven Tsengas, President


                                              Witness: /s/ John G. Murchie
                                                       -------------------------
                                                           JOHN G. MURCHIE