Water Temp and Nutes Temp

1)When using RO water what is the best way to warm to temp?
2)Add nutes before or after warming of water?

I keep my water in my grow room, that way it is the same as the air temp in there. As long as it isn't ice water temp isn't that important in my opinion. Nutes can be added anytime to water. I keep 10, gallon jugs of water on hand for 12 plants.

i use a sump pump to mix my nutes and transfer them so i just use the pump to warm the water up. for 25 gal it usually takes about an hour or a little less.

What is a good heater brand?