The number and size of colonies found in bacterial counts of sea water collected from the Menai Straits varies with the concentration of peptone in the medium. The optimum concentration of peptone was found to be 0.3%. Neither yeast extract, beef extract or added iron increased the count when added to media made from Menai Straits water. The effect of various temperatures on the count, and the relative merits of pour plates and surface growth techniques were examined. Vigorous shaking, or passage through a Sharpies centrifuge, was found to increase the count.