hard to replace expereience if you have any amount of phyto and it is sunny it is strange to not see oxygen levels in excess of saturation. If it lower than saturation that afternoon it is a sign somehting is up and warrants further investigation. I look at percetn saturation almost as as I do obsolute values. We for sure look at saturation levels in our fish hauling tanks, if going to less than 100% you best figure it out in a hurry unless deliverying fish straight to the frying pan.

Greg Grimes
www.lakework.com