If he has a fuge, which I heard no mention of, then he can leave the fuge light running. Either way leave tank lights off while cycle spikes. When cycle is complete do a water change and good to goif he leaves the lights off now, what will happen when he turns them on ? what is absorbing the phosphate from the tap water while the lights are off?
it doesn't just disappear overtime. unless of course he doesn't run lights over his tank ever. just common sense, he needs nutrients. he doesn't need excessive phosphate that comes with with tap water