If your temperatures are 79-82 root rot is almost inevitable, and rot will be a very quick way to lose
your entire crop.
Things you can do to help lower reservoir temperatures:
-Lower room ambient temperaturer (assuming they're higher as the res shouldn't be that much different from ambient)
-Use a fan to run over your reservoir water
-Insulate your system and reservoir with reflectix or something similar
-Use frozen water bottles to set inside your res to lower temps (pain in the ass, but effective)
-Water chiller (easiest/most effective but costliest by far)
There are also addatives which can help you clean things up from rot as well:
-Hygrozyme will help break down waste in your reservoir for the plants to use easier
-h2o2 will help things whiten up and clean up as well, don't use too much. Also don't use
this if you're using beneficial organisms in your reservoir as it will kill them off. But chances
are there are no beneficial organisms if you're facing root rot.