what is the optimal temp for water

Im brand new to hydro and Im running the aeroflo 60 with a 600 hps and im not sure what the optimal temp is for the resivoir... I guess It was never even a concern until I was reading through some posts on this website and seen that people needed some water refridgrant. If somebody could tell me the best temp I would greatly appreciate it...

Looks like you should keep it under 70 ....Are you using all 60 sites? How is it with a 600 in there? Do you want to get more more light second time around?