ambient room temperature in relation to reservoir temperature...

What temperature does my room need to be, to keep reservoir at 68 degrees. ...???

try a water heater like the ones for fish tanks to keep your nutes in the right temp my room is 25-27 depends on the time of day and around 20 when lights off

You don't want to change your growing environment for the plants to accommodate the res. You want to control the res temps separately. If your res is too warm, and you don'thhave a water chiller, add a frozen 2 liter of water to the res. If it's too cold, like under 62f, then you need a water heater.

So your saying that if my room is at at 74-77 degrees" all the time" my res temperature wont be the right temp....I haven't had to grow for patients in awhile. ..but yeah I used to keep sum ph balanced ice for temp control. .its works...but this particular grow site is a quite sizeable and needs to be absolutely dialed in, as per request. Funds r not an issue....I thought I read in the "Cervantes bible" that there was a relative air temp that if maintained, that the res would the right temp??

I would highly suggest a water chiller for a larger grow. I'm sure there is a ambient room temp to control the res temps, but I'm guessing it would be 68 which is too cold for the plants during the day.

A cool concrete floor will help drastically though, but it's best to keep the temp in the res stable and that wouldn't be possible by using the ambient room temp. You'll want the day time temps 77ish (a little higher with co2), and night time temps 68ish(which is perfect for res temps). You'll be fine at lights out with out running a chiller, most likely, but day time the chiller would need to cycle a few times. 68 degree water temps is the higher end also, I like 65, which would be impossible to achieve through ambient room temp