dr_sudz;4153610; said:Koi can easily be in warmer waters of 75+ that is when they are most likely to respond to spawning. Anyone who has an outdoor pond can attest to the fact that when the summer heat is up the temp of the pond is up. If you can't maintain the heat then don't.
Good Point, many Koi keepers heat their ponds to acheive higher growth rates BUT the key as you say is stability.
I was only thinking today...lets assume a Koi lives 40 years but goes in to "hibernation" every winter with a massive slow down, would they only live 20-30 years if we heated their water all year (It would be easy for my pool heater to heat a pond too)