To identify bacterial natural products that inhibit formation or disrupt pre-formed biofilms from P. aeruginosa and S. aureus, we screened a library of 810 chemical fractions of 140 bacterial strains isolated from primarily moon snail egg collars for biofilm inhibition properties. Although several fractions inhibited biofilm formation in S. aureus and P. aeruginosa, only two active fractions inhibited biofilm formation in both organisms.