68f is believed to be the optimum temp'. Anything more is warmer, anything lower is colder. You've made an excellent point though. What do you class as warm?
68-74, I can control my heat as low as 68. Under that and I have to pull the heater out before it shuts off automatically.
I am not disagreeing with you, but why would ppm be higher in cold water?
Because during the week that the water was in the high 40's low 50's, the plants did not take up the nutrients, so when fresh water was added, the ppm's were not far off what they were at the beginning of that week.
i have been just toping off with just plain water and when the ppm drops about 100-150 i add nutes to bring up to par. right now im slowly decreasing and its at 1050 right now. maybe it is because of salt build up because i am unable to clean the inside of the res. i can only drain it out and fill it back up with fresh
solution
Have you heard of a product called FloraKleen? Every other week I clean my Res with 250ml and 250-500ml of FloraShield "depending on how much I have at the time!" I run this for 3 30 min cycles in between nute changes. I see a rise of about 3-4oo ppm after 3 cycles. This leads me to believe that I have taken out most of the salts that have built up during the two weeks of feeding. Now I can add fresh nutrient and my ppm is not a reading of left over salt build up...It take alittle more time, but, I think it is worth the work. I have a Ebb n Grow set-up, the basic layout of this system is a 50 gal Res, and a control unit that controls the height of the water level and the time of the feeding. They say that one controller can feed up to 48 buckets, but my experience was not satisfactory with that many. I like to use up to 36, so I like to grow medium size plants in this system, 3-4'. I have two controllers so my room is well packed!