In the United States, populations of nonindigenous Pomacea spp. have been reported in at least 10 states, and the rate of spread has been greatest in the southeastern United States, particularly in Florida. Factors impacting successful establishment of molluscs include salinity, pH, and desiccation tolerance. This article reports on median survival and growth of Pomacea canaliculata and Pomacea maculata (hatchlings through adults) in 28-day trials focused on these factors with an ambient condition serving as a control (e.g., 0 = salinity control). Overall hatchlings had the lowest survival, followed by juveniles then adults. Median survival was less than 28 days for all salinity treatments greater than 16. Median survival was 28 days for all pH levels (5.5–9.5) for juveniles and adults of both species. Median survival in desiccation treatments (>80% relative humidity and wet sand or <60% relative humidity and dry sand) was 28 days for adults of both species and for juvenile P. canaliculata. The closer a treatment was to the control level, the greater the increases in shell length and width. In all treatments, snails experienced a loss in mass; the closer a parameter to the control typically resulted in the greatest loss in mass. The ability of these species to tolerate such diverse conditions will leave many systems vulnerable to invasion.