The purpose of these studies was to determine if the number of species colonizing artificial substrates is related to the depth of water at which they were suspended. Two series of 7.6 cm x 6.4 cm x 5.1 cm hexahedrally shaped units (PF units) of polyurethane foam were suspended at the surface and at 1.5, 3.0, 4.5, and 6.0 m in South Fishtail Bay, Douglas Lake, Michigan at a point where the total depth was 6.5 m. A third series was suspended at 6, 11, 12, 13, 14, 15, 18, and 20 m where the total depth was 20.5 m deep. The thermocline was between 6 and 10 m for most of the study. There was no pattern evident related to depth of substrate suspension for the PF units in the epilimnion which had an average of 35.4 species per PF unit. Those in the hypolimnion had an average of 11.4 species during the summer stratification. However, these differences were substantially reduced by the fall overturn of the lake which was followed by an average of 31.4 species per PF unit in the 11 to 20 m depths.