The microbe tea is all well and good but I never needed it and I wasn't able to keep res temps below 83 F near the end of my growing season. This was in a room with 6-20 gallon rubbermaids containing monster trees and 2400 watts overhead in a 12 x 10 foot room. What worked for me was copious aeration. Even though there is only a certain amount of dissolved oxygen that can be held in solution for a given temperature that doesn't mean that the maximum dissolved oxygen capacity for a body of water at , lets say 83 degrees ( or even higher for that matter) isn't more than adequate for even the most giant root ball. The only way to rule out that the temperature is too high for adequate root growth is to agitate the air/water interface to the max .In other words just stir it up as much as possible without water spilling out of the res.If that isn't enough to keep the roots from turning dark brown and slimy then the microbe tea is your last resort. Although, I certainly agree that the microbe tea is the first course of action once the damage is already done.