Aerating the resivoir??

I just read yer not suposed to do that,is this true??

what? I'd say if you didn't you may get fungi. The bubbles are a good thing bra.

so maybe an air stone in a 140 liter tank?

You can have many airstones the roots love it!! as long as the water appears to be fizzing not bubbling like a saucepan, I take it your in Hydro, what method are you using DWC, EB N FLO etc etc?? a fogger with float is also an excellent method, look into that, it has lots of benifits including rapid growth! - Stelthy

bubbling like a saucepan is fine too