Updated: Sep 3, 2020
At this time, the use of purple non-sulfur bacteria (PNSB) for bioremediation of agricultural water assets is most common in East Asian fish and shrimp farms. So, it shouldn't be surprising that much of the research in this area has been coming from that part of the globe.
Thus far, most of these studies have been carried out in a tight and tidy laboratory setting. In a paper published by the China National Knowledge Infrastructure (CNKI), researchers demonstrate the efficiency with which Rhodopseudomonas palustris (strain CQV97) sequesters dissolved nutrients in the "complicated water environment" of an aquaculture system. Findings in the study suggest that when fed a higher-molecule organic carbon source (such as acetate or ethanol), R. palustris very aggressively consumes ammonium, nitrite and nitrate.
Purple non-sulfur bacteria are highly applicable for marine aquaculture (and especially for coraliculture) where low nutrient levels are commonly maintained through carbon dosing. Unlike the obligately aerobic bacteria that are normally targeted, PNSB additionally consume carbon/nutrients in anaerobic environments, thereby competing with microbes that produce toxic metabolites (e.g. hydrogen sulfide). Unlike nitrifying and denitrifying bacteria, they are capable of performing photosynthesis. Even more, they have been demonstrated repeatedly to possess strong probiotic properties that promote the health of diverse aquatic species. Ultimately, as they are consumed by bacterivores (protozoa, rotifers, copepods, sponges, corals, bivalve mollusks, etc.), they pass essential biomatter (proteins, vitamins and pigments) along the food chain.
As more and more encouraging findings continue to be shared, it's quite likely that PNSB will increasingly catch on with Western aquarists and aquaculturists.