It's been a while since I've dealt with pythium/root rott, but I remember the PH climbing erratically, and there would be growth in the res as well as on the roots, usually slimey nasty stuff. Flood and drain did away with these issues for me, as did the chem nutrient/ H2O2 combo. What type of system do you use?
when the rez temps go over 70... you can have problems. Earl used to run his pumps constant, which would produce more heat... plus, he's anal about his temps.
I guess SB never has problems with high rez temps, i dont know.
Nutrients also come into play, if you go organic nutes, then you'd have to use hygrozyme at first sign of problems (funk in the rez or slime on roots) but if you go chem nutes, you can just use Hydrogen Peroxide as a preventative maintenance type of thing. I use Chem nutes and H2O2, simple, and cheap.