Laboratory observation on the larvivorus ability of Poecilia reticulata was carries out by SASA et. al in Bangkok. 1965. This is a similar preliminary observation on several species of fishes, commonly found in Indonesia and known to have larvivorous habits. The objectives is to find which species can be utilised as a biological agent for larval control. It was observed that all fishes like to prey on mosquito larvae. The average numbers of larvae per fish consumed during ten days observation are : 86,5 for Trichogaster trichopterus; 29,4 for Ctenops vittatus; 22,3 for Dermogenys pusillus; 22 for Poecilia reticulata (female); 1 7,2 for Poecilia reticulata (male); 48,6 for Rasbora lateristriata; 52,8 for Punctius binotatus; 36,6 for Panchax panchax.