I changed the res yesterday (10 days between changes) but it took all evening to refill. RO water 6.40ph. After I added the nutes 4.50ph.
Ph is at 4.90 in the morning (7 hours later). Also, the morning temp in the tent is around 62-65f degrees. 50-55 RH. It gets up to 75f by mid day. How bad is that? I dont have any PH-UP yet. Im headed to the hydro store in a few minutes. Ive always had to use PH-DOWN. Figures. 1210ppm
Should I use the Growtek Silicosis & SM-90 on every res change? Or every other?
Have you callibrated your pH meter lately?
RO water should be right around 7.0, +/-.15 at the most.
Sounds like you need some calibration solution (although picking up some pH Up can't hurt).
And are you running your light 24/0? And does your light have its own air-cooling fan, or is there one fan that cools the light and also exhausts the tent?
Either way, I'd get a thermostat like this:
http://www.luxproducts.com/thermostats/win100.htm
I just got one and I love it - had the same problem, sometimes the ambient temp in my garage is so low that I don't need to run the fan cooling the light, so this thermostat shuts it off to keep heat inside the tent.
Especially if your exhaust fan(s) are always running, that'll at least keep the temps ~70 for you.
Regarding the SM-90, I have some but have never opened it - I'm saving it for when I (hopefully never) really need it, as I feel that feeding low "preventative" doses will just harden off the mites (or whatever else I'm trying to kill).
I basically use H2O2 (35%) as my preventative in my rez, kills everything.