Ok man i guess i couldnt of come across your thread at a better time. So i had some res temp issues just like you and i got root rot. I used some hydrogen peroxide and just plain water and super cleaned the res. Everything cleared up and looked golden after 2 days. I switched the res out and added my nutes for flowering last night. Everything looked fine. Now tonight my lights just came on and i look and i have that white gunk all over my roots like the snot stuff you had in your res. What the hell is this from how do i kill it? My plants look perfectly healthy and are still growing but my roots are not getting well established and its one problem after the next with them. my res temps range from like 66-72 now so i dont think its the res temps i have no idea what the fing problem is. What was the problem for you? Was it just res temps? My roots went from being a nasty brown to clearing up to now having this super white snot shit all over them please help!!
It can be one of two things in my experience: Algae or bacteria. Pythium ( root rot ) is a dirty fucking whore of a bacteria and often it can follow you around until your crop is finished, and afterwards if you dont sterilize everything. Even if you hydrox your shit, if some of that bactera survives and the reason it happened isn't solved, it WILL come back. My advice to you in this case: Go buy sensizym and piranha from a hydro store and start using that this crop. Try and get your res temps even lower. Use frozen water bottles like me. Disinfect the bottles, your tools, your EVERYTHING before it goes into the res. Sensizym and piranha literally rescued my crop dude, seriously think about it. Also, if you use beneficial bacters such as sensi or piranha, you have to drop the hydrogen peroxide completely, it will obliterate them. If you buy the BB's, consider voodoo juice as well. It'll make your roots thicker than your forearm. Good for rescuing a grow (expensive as fuck though)
Make sure every week when you change your res you shop vac the old shit out. The water pump does a piss-poor job of getting all the old crap out of there, you need to get the last bit yourself. And all the really bad stuff like dead roots and rot is sitting at the bottom so, if you leave it to the water pump, youll be seeing that till the end of your grow.
If it's algae, which I battled with a bit, it's because of light leaks. BCNL likes to advertise that their boxes are lightproof, but they most certainly are not. I'm not talking just about the net pods either. I don't have your journal open, but you absolutely need to (at the very least) put tin foil over the tops of your baskets so that no light leaks through them. You can save yourself a lot of trouble by putting a giant sheet of mylar across the top of your grow, but you might be too far into it (as I was) to do this.
The best thing you can do for algae is to go into your box, turn the lights out, open the lid of the res open and poke your head in there, then run a flash light over the top. If you see ANY light, it needs to be fixed, pronto. Algae CANNOT live without light. The slime for me was algae, i light proofed my box then cleaned the shit out of my res, and it hasn't returned. By the way, when algae dies, the pythium bacteria can it it and multiply. These two problems are almost synergistic. Once the light leak is solved, disinfect a brush and scrub your air stones and box clean of any slime (not the roots). Suck all that shit out, and once the problems solved that should do it. The shit in your roots you might have to either do a hydrogen peroxide dunk (if its really bad) or just gently rinse off with water... or leave it. Your roots might clean themselves off in fresh nutes if the algae can't reproduce.
Remember: you can treat the problem all day long, but if you don't solve the source of that problem, you'll never see the end of it. It cost me a crop, I hope it doesn't for you.
Please take some to-date pictures of your root zone, res, plants and everything and post them on your journal, then hollar. I'll take a look and give you my opinion on what you're dealing with.