Theri hunger closely is linked to the temp as Cecil mentioned. When it jumps into the mid 40's and then into the 50's, their appetite will start spiking. 55-65 is the range when their metabolism is full cranked up and they grow the fastest. The rule is whater they can eat in 15 minutes is close tot he correct amount. That said, I do refere to formulas on trout feeding and if there is one thing I ahve learned about feed rates is- it is better to slightly underfeed them, to avoid the diabetic like condition they get when over feeding.
And, I learned that when the temp rises to the dangerous 68- 70 + range, ratchet back feeding to much less, as mass feeding reduces oxygen at this temp and the water is already struggling to keep enough o2 in it at that temp.
