Quote Originally Posted by Zandor
Not quite correct. Stems sitting in water can and will rot to some point and that will slow if not stop rooting. It's best to have them above the water line and the bubbles will feed them by capillary action. There is a big difference.

You are correct about the light entering the rez not only will the roots die from light but alga will also grow and that will eat up the oxygen the roots need to grow.
i ran a diy bubbler for a while and always paid attention if the stems above or below the water rooted faster and there was no difference ever. sometimes the ones above rooted first and sometimes the ones below did. what i did notice was that the stems below the water tend to bend up out of the water anyway because of the upwards pressure of the bubbles. i had 100% rooting with the bubbler, not one cut ever rotted. i made the statement about it not making a difference from personal experiences. others may have had different results but as far as i'm concerned it doesn't matter, above or below the waterline is all the same. i have the utmost respect for you and your opinions zandor, i am sure what you are saying is correct, as i said, i am going by personal experience which is not the same for every grower. however i do know that if you have the water level too low and not enough bubbles then your cuts will wilt and die, so if you do keep all stems out of the water make sure that you have enough airstones in the resevoir. good luck