Growth and survival ofCyprinodon variegatus, Fundulus heteroclitus, Menidia beryllina, andLucania parva, held in combination with an omnivorous grass shrimp–Palaemonetes pugio, and a predatory diving beetleTropisternus lateralis, were measured at 12–60% in outdoor static microcosms that simulate salt marsh ponds. We predicted that the low species richness of this abiotically harsh but highly productive habitat would lead to a high degree of interaction among species. The presence of the beetle had no effect on the fish or the shrimp. Removal of the shrimp similarly had no detectable effect on the fish. There was a trend in proportions of survival among three fish:C. variegatus>F. heteroclitus>M. beryllina. Survival ofM. beryllinawas greater when it was alone at low densities of its own species (333 v. 667 fish m−3), and less when it was paired with F.heteroclitus. Interactions with other species diminished the growth ofM. beryllina. Survival of F.heteroclituswas greater when it was alone at low density (333 m−3), than when the same number were placed together withMenidiaandCyprinodonat a total fish density of 999 m−3. There were no effects of removal of other species on survival or growth ofC. variegatusat either 12′5 or 24%. This study showed that a complex array of interactions occurred among six common members of a salt marsh food web, but the degree of interaction Was less than W