A survey of the algal flora for a minimally polluted stream in southeastern Ohio was conducted over a two-year period (17 sampling dates) as part of an all-taxa biotic survey. Four algal categories were sampled: macroalgae (readily visible with the naked eye), microalgae (associated with macroalgae), erosional periphyton (microalgae from riffles), and depositional periphyton (microalgae from pools). A total of 217 infrageneric taxa were collected. There were 25 cyanobacteria, 74 chlorophytes, 6 chrysophytes, 3 cryptophytes, 86 diatoms, 4 dinophytes, 12 euglenophytes, 1 raphidophyte, 3 rhodophytes, and 3 tribophytes. A seasonal trend was observed in species richness; fall had the most taxa (136), followed by winter (107), summer (100), and spring (82). Approximately half of the taxa occurred in samples from more than one season, but only 15% were present year-round. Overall, species richness was not correlated to any stream parameter. However, diatom species richness was positively correlated to pH, and both diatom and soft-bodied algal richness were negatively affected by nutrient loading. For the soft-bodied algae, the microalgae category was the most species-rich followed by the depositional periphyton, erosional periphyton, and macroalgae. For the diatoms, the depositional periphyton had higher species richness than the erosional periphyton. Five diatom and 17 soft-bodied algal taxa previously unreported from the Unglaciated Western Alleghany Plateau were identified from this stream reach. This study highlights the need for multiple samplings in different seasons to capture the total species richness, since only a small fraction of the taxa were collected year-round and one third of the diatoms collected were rare.