The catfish trematode (Bolbophorus damnificus) is a problem in the catfish industry in the southeastern USA, resulting in significant economic losses. The life cycle of B. damnificus consists of a planorbid snail as the first intermediate host, catfish as the second intermediate host, and the white pelican (Pelecanus erythrorhynchos) as the final host. The marsh rams-horn snail (Planorbella trivolvis) is recognized as the common first intermediate host of B. damnificus. Controlling populations of this snail species in aquaculture ponds can significantly reduce the infection impacts of B. damnificus. Among molluscicides, copper (Cu) is an effective treatment agent for pond snails. Previous studies found that marsh ramshorn and related species were sensitive to Cu. However, the effect of Cu on snails is dependent on water quality, such as temperature, pH, hardness, alkalinity, total suspended solids, and dissolved organic matter. While these water quality parameters in aquaculture ponds vary geographically, research on the influence of water quality on Cu toxicity to these snail species has not been conducted. This study examined the influence of water quality on Cu bioavailability and toxicity to the marsh rams-horn snail. The standard 96-h toxicity test was used to determine the toxicity of Cu on the snail. The initial results found as hardness increased, Cu toxicity decreased during the first 24 to 48 hours of exposure, likely due to more competition of hardness ions with Cu at the biotic ligand of the snail. The 24-h LC50 increased from 265 µg/L Cu in soft water to 652 µg/L Cu in hard water or 510 µg/L Cu in very hard water. Interestingly, the LC50 values remained similar for all hardness levels when the exposure time was increased to 96 hours. These results suggest that the snails may have reached their Cu threshold by this timeframe regardless of hardness. More research needs to be conducted to understand this interesting observation and determine the influence of other water quality characteristics on Cu toxicity to the marsh rams-horn snail. The effect of hardness water quality parameters on Cu toxicity to the snail will be presented.