Heres how an old chinese guy explained it to me . Lest look at it from a fishes point of view . Ever wonder why some fish in wamer water climates , gulp air ? Its due to the FACT that water over 72 degrees looses its ability to retain oxygen . Thus higher than 72 degrees is not real bad , but 78 would be terrible . Ever notice most fish kills happen in hot water ? Optimum , from what ive experienced is somewhere round 65-70 degrees is usually pretty good .
Have you ever jumped in 50 degree water ? What does it do to you ? Shock right ? Same thing happens with ice cold water on roots ... say your in Florida , on a 90 degree day and you jump into blue springs , which has a constant 70 degree water temo all year round . Itll make yer balls shrink let me tell ya , and your nipples almost explode . SO if youve got a 75-80 degree grow room and your dumping 50 degree water into the roots ..... well ? SO kiddies , from what ive read and talked , and eperienced ..... 75-80 on your room temp , keep that water round 67 . If you can . BUT please dont let it get into the mid to upper 70's , 80's . Might as well throw away that air pump . AND oh yeah , if your using organic nutrients as well , they just get nasty , smelly and want to ferment , QUICKLY over 75 degrees .