You'll actually supposed to water with a temp of <70, within reason, supposed to allow the plant to uptake the nutrients easier if I remember correctly. Could be total BS though haha Oh didn't even notice this was hydroponics section haha, you want the water in the reservoir a max of 65. Else root rot and mold can become a concern.
the lower the temp the more of an oxygen issue you,ll start having in any hydro ,b-bucket ,ebb n flow , nft, system. Saying that it depends on what your actually concerned about? is it when lights are off your worried with temps or lights on or both? can have temps as low as 10c (50f) but now this is where oxy levels & ppm comes into play big time , not desirable but maintainable having temps so low , your really wanting temps around 18-24c lights on & say around 12-18c+ lights off is perfect temps if attainable? (MY DESIRABLE TEMPS , NOT CAST IN STONE PEOPLE ) So just a wee bit more info my friend , if needed , about your concerns , is it your constant temps or lights out temps , or both that is bothering you. What a can of worms your question can open as especially hydro,DWC,EBB N FLOW , NFT , growers can gain absolutely tremendous results if temps are maintained throughout the grow properly or drastically be reduced by temps all over the place. Will keep an eye on this post as im sure you,ll get all sorts of differing answers/comments regarding water temps. Too cold can shock your plants but as temps rises it will get to the optimum temp desired which roots love & reward you for being so nice to them up to you to try maintain they temps But in answer to your question , They can withstand quite low temps , not recommended , & still come on but optimum temps should be around the marks already given earlier in my post , in my humble opinion !! All the best Peace
Air temp is a concern, keep it below 85 and try to have your night time temps not go more than 10 below lights on. 75-79 is your optimal temperature zone. Anything below 55 is risky for your plants. I've always used cold water or water out of the refrigerator to refill my reservoir and drop temps to bring out a strain's colors. I don't have a scientific answer to this but in my experience cold water doesn't seem to bother the plants. I wouldn't be comfortable with the res going below 50 degrees but pouring cold water in the res and directly on the roots seem to be fine. I'm sure someone will have a better answer than me but I've always tried to keep my res comfortably cool.
the room temp is at 76f. my water is at 65, during day. during the night it sits at 58. so im guessing im good to go, right? thank you guys for your positive comments. I like them all. I am about to smoke a fatty for you guys.lol thank you all!