Everybody who says plain ice chunks will lower nute levels wtf kinda tiny rez are you guys running ?
Before i went geothermal to cool my rez's i would dump a whole party store bag of ice in my 55 gallon rez & it would only lower the ppm the smallest amount,like 5-10 ppm !
Do you have to add water daily to top off the rez ? If so use ice instead of water & you killed 2 birds with one stone.
If you can afford it get a rez chiller & it will pay for itself the 1st harvest,having a steady rez temp below 60 degrees for the entire grow pays off fast.