timed Powerheads?

[Aquaria]

well i have been wondering the same thing, because of the way i have setup timers for lights was easy for me to time my flow. at night i have my eheim 2217 turn on for carbon phos and denitrate so i decided to turn off my nano (have koralia 1 and a nano in a 46g bow), so i could mantain as close to day as possible only 40 g/h difference more at night .but im wondering if i should leave both on all the time and keep my canister on the timer