I like all these comments lol..
Great news on your HSB, but you may not like my comment.
I would be on the cautious side of thinking your DO is that high.
This graph represents the solubility of oxygen in water at various temperatures. This is based on 1 atmosphere of pressure.
Any reading on the right side of the red line requires increased pressure to achieve. In your case, you would be about 1.5 times atmospheric pressure, or about 23 psi.
Not saying the measurements taken are incorrect, just saying to be a bit cautious.
You can take DO readings around diffusers, and they will be higher, but DO will quickly find a new home in water that is not in a supersaturated state, under increased pressure as yours appears to be.
