Climate models predict that the Caribbean will be greatly affected over the next few decades, leading to increased droughts in the region. Droughts can greatly affect stream food webs and ecosystem function, particularly in tropical rainforest environments. In oceanic islands, shrimp often occupy the top level of these food webs and exert strong top-down controls on other trophic levels, making their interactions with droughts important to understanding ecosystem function. In particular, shrimp play a large role in controlling the abundance of fine organic matter, algal biomass, and meiofaunal communities due to their role as omnivores. Our objective was to assess the role of shrimp in mediating the responses of periphyton to an experimental flow reduction in tropical montane streams. We studied an aseasonal tropical rainforest stream in El Yunque National Forest in Puerto Rico, Quebrada Prieta, which has two tributaries. One tributary was left with natural flow while the other contains the long-term StreamFRE project which reduces flow by 40%. Within each tributary, four pools were identified, each containing an electric exclusion quadrat to keep out shrimp as well as a control quadrat. Chlorophyll did not show a significant difference between the flow levels or the treatments. However, there is a clear trend of higher chlorophyll in the shrimp exclusion treatment. Shrimp absence did have a significant effect on sediment levels in our natural flow stream, but not in our low flow stream. Flow had a significant effect on meiofaunal communities, while shrimp presence did not. This may be explained by the flow levels but could also be a result of differing stream geomorphology. Overall, our study supports previous research showing that shrimp are major consumers in tropical streams and their presence swamps the effects of other factors, like our flow reduction.