changin water every 2 weeks?

im using a hydro setup and i was told to change the water in the buckets every 2 weeks
that was from a company that was selling me powder nutrients which makes sense cause the water can get nasty with left over powder residue from weeks on but now im using a liquid nutrient and i cleeaned and put fresh water in my tubs
the question is do i still need to change the tubs with fresh water every two weeks?
im not sure if theres a problem with leftover water at the bottom of the tub can hurt the roots?
thanks for ur help

any help would be great

I would change the water more like once every 10-12 days. A lot of it will evaporate and even start to stink. You're gonna wanna give yer girls FRESH nutrients. If you don't you will see salt build up and other problems that can turn nasty. Don't be lazy, change that water. Your girls will thank you.

im in a DWC setup that with the chiller is about 15 gallons, I change the water once a week the setup has 9 spots and i have a 4 inch air stone under each plant. Its like a root jacquzzi in there but i keep my water between 62-65 F changing every week is excessive but like Train79 said your girls will love you for it. i have a good system when the water evaps the ppms go up so i start low and they raise to where i want them and then do my water change!

if water temps are good and you dont have a overloaded res meaning to many plants then 2 weeks is ok no longer,
if any of the above is a factor the go with every week. water temp is the biggest enemy!

gotcha guys thanks