I’ve been researching and building my aquaponics business for about a year now–I’ve built a functioning prototype, grew some test plants, etc, and have been demineralizing my fish effluent in a separate tank with a large airstone. In my research, I came across discussions about azospirillium bacteria, and how it has been used as soil additive/ inoculation in South America. My question for all is this: is it possible that azospirillium is active in fish effluent water? I know there are many, many types of bacteria present in demineralized effluent; is it possible that azospirillium is present as well?
Without getting into details, I would say there is a strong possibility that Azospirillum bacteria are present in your system, but you would need to do some gene sequencing or a microbiome assay to confirm it. What pH and Temperature are you running? That could give some clues. That said, I’m not really sure how much it matters. In a healthy aquaponics system, your microbiome will naturally become quite diverse. Plants often influence their root zone microbiome through exudates, selecting/promoting for the microbes that benefit them - which is probably outside of our control.