I would have to say yes in the fact that water could get to hot like ewest said and slow eating down. I have expierenced this first hand this year on my pond. Even to hot maybe to kill some sensative type fish also. From what I been reading thats another reason why you need to be careful when you start to circulate or airate your pond as the water temps in the different levels of the pond could effect your fish as well once you start to mixing it all together.

RC51

The only difference between a rut and a Grave is the depth. So get up get out of that rut and get moving!! Time to work!!