I would say age tap water as short of time period as possible, the longer it is in a holding container the more time un wanted bacteria gets a chance to form and build up and this can cause all types of problems and leave you sctraching your head woundering what is happening to your fish, fry even more so.
I would test your water straight from the tap and after you have your water container full add a airstone or a water pump droping the return water from a foot or so back into the container and see how long it takes for the ph to drop complety and stay steady non bouncing. and take note of how long it took and you will know then it is ok to use and after that time frame storing the water only gives time for bacteria to start.
I use a pin point ph moniter and after 30mins my ph has settled and usually if I dont use the water after 12hrs I will discard it.
if the water in the container is cloudy you know you have let it set to long and not to use it.