Not an expert and JH may have a better answer but yes 24% is high and unachievable without supersaturation (adding pure O2). It is my understanding that if you can provide 8-8.5 % you will have very happy roots. You can achieve this by flooming, air stones, or Venturi. Keep in mind that temps would have to be kept at 70 or below (I think lol) to achieve these levels using the above methods. There are charts available that tell you what the saturated levels are at different temps and altitude (re sea level or above) also I believe EC levels play a big role and the higher the lower the saturation levels. That is why over feeding is a bad thing beyond burning the shit out of plants. Perhaps if I have stated any bullshit JH could clean it up, this is just what I have researched (limited effort lol) when I was not being proactive and almost lost my crop.

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