Enhanced biological phosphorus removal (EBPR) involves the cycling of biomass through carbon-rich anaerobic (feast) and carbon-deficient (famine) conditions, promoting the activity of polyphosphate accumulating organisms (PAOs). PAOs utilise aerobically stored polyphosphate to energise the anaerobic uptake and storage of volatile fatty acids (VFAs) as polyhydroxyalkanoates (PHAs). However, several alternate metabolic strategies are possessed by other microorganisms, which can compete with the PAO for carbon at the theoretical expense of EBPR efficiency. The most studied are the glycogen accumulating organisms (GAOs), which utilize aerobically stored glycogen to energize anaerobic VFA uptake and storage. The historical understanding of EBPR microbiology has been that VFAs are made available to the PAOs and GAOs through the hydrolysis and fermentation of more complex substrates by fermentative microorganisms. The application of community profiling and single-cell analyses to full-scale systems has dramatically changed our view of the microbiology of EBPR. This has principally included the discovery of the fermentative PAO Tetrasphaera spp., which often outnumber classical PAOs in full-scale systems. In the presented study we coupled Raman-microspectroscopy with fluorescence in situ hybridisation (FISH) to quantify internal polyphosphate stores in situ to estimate the relative importance of the fermentative Tetrasphaera and classical PAOs for the first time - finding that they have equal importance in Danish full-scale systems. We also found that members of the putative GAO Micropruina spp. also possess a fermentative metabolism and accumulate glycogen, but not PHA or polyphosphate, anaerobically in full-scale EBPR systems. We propose that the fermentative PAOs compete with other fermenters for sugars and amino acids, and the classical PAOs and GAOs compete for fermentation by-products, such as VFAs. Also, any carbon stored by the fermentative organisms is not available to the classical PAOs under anaerobic conditions. These findings indicate that the current models of the competition between PAO and GAO in EBPR systems need to be revised to account for the impact of carbon and phosphate storage by fermentative organisms.