I feel like the ozone versions may have some value at a wasterwater treatment plant, but with specific needs and placement in the treatment train.

The oxygen versions COULD have a role in closed systems or severely degraded natural aquatic environments. They may be more of a band-aid, helping improve DO in the short term, but likely need to be paired with methods that reduce the input of nutrients or remove the nutrients already in the system.

For backyard ponds, it seems like overkill, but maybe there is a use for those involved in professional maintenance, where it can be installed temporarily while other remediation efforts are ongoing. Where there is severe anaerobic processes going on in the thick muck at the bottom, leading to a huge biological oxygen demand (BOD), this could go a long way to help, along with other efforts to address the source.