Question about proper Twinstar (Chihiros Doc / O3 generator) usage regarding O2 saturation

Hello,

I have a 9g high-tech tank and a Chihiros Doctor rated for 3 sizes - under 60L (15g), 60L-90L, and 90L-120L. Obviously I'm using the lowest setting per the recommendations, but I wondered what would happen if I were to use the 60-90L setting. I am primarily using the device to increase O2 (using a canister and surface skimmer - not very high O2 saturation) and the tank is somewhat tall and narrow so there's not much surface area at the top of the water column to get good gas exchange. In Tom's Wallichi journal he mentions "if used correctly" these devices increase O2 something like 10-20%

Considering I have no critters in this tank, would using the higher setting be harming anything, or just adding slightly more O2? Or would too much be detrimental in some way, possibly to the beneficial bacteria in the filter?

I couldn't find much discussion about the benefit from using devices like this so any discussion about their use specifically for O2 would be fantastic. I am trying to stay ahead of some BGA creeping up around my foreground, it is taking 3-4 large water changes a week (Newish ADA soil) to keep it at bay - would increased O2 help keep this under control at all?

edit* Dosing modified EI because of new ADA soil and frequent water changes. About 2/3rds EI + extra scoops of NO3 and K after each water change. High on micros/iron.

 

edited main post to include dosing thanks!