In a series of bioassays, four planarian species—Dugesia dorotocephala(Woodworth),Dugesia tigrina(Girard),Cura foremanii(Girard),Dendrocelopsis vaginatus(Hyman)—were evaluated against six water quality parameters (hardness, temperature, salinity, pH, dissolved organics, and dissolved oxygen) for effects on species survival and asexual reproduction. No significant (P<0.05) effects were determined on survival and asexual reproduction of three species exposed to various levels of hardness.Dugesia tigrinawas determined to have a significant increase in asexual reproduction with an increase in hardness. Dissolved oxygen was determined to be a critical parameter affecting both survival and reproduction of the species evaluated.Dugesia dorotocephalaandD. tigrinawere determined to be the most adaptable and tolerant of the species evaluated.