Eutrophic lakes suffer from frequent harmful algae blooms, and while many management decisions in the past focused on reducing phosphorus inputs, research shows that phosphorus, nitrogen, and their ratios are all important to consider. Diatoms are often used to monitor water quality and indicate environmental conditions. In this study we used benthic and planktonic diatom communities in Lake Okeechobee, FL to better understand how algal communities differ in their responds to different TN:TP ratios. We conducted an observational study at three habitats within the lake with differing TN:TP ratios; the C-38 canal, the Northern pelagic zone, and the Indian Prairie Marsh. We measured planktonic and benthic algal biomass, diatom richness, and examined the diatom assemblages to find taxa indicating for different values along a water and benthic TN:TP gradient. The habitats showed strong TN:TP gradients across sites, with both planktonic and benthic algal biomass and diatom richness declining along the gradients. We also found that diatom assemblages separated by habitat were mainly driven by nutrients, and taxa did a good job of indicating a range of values along our gradients. Our results imply that the three habitats we sampled are regulated by nitrogen and phosphorus differently, and diatoms in the lake can be used to monitor TN:TP. Diatoms are able to indicate and potentially predict harmful algae blooms, as blooming algae have favorable TN:TP requirements.