My 250 gallon outdoor pfr pond must be really unhappy now, haha, it's probably 48 degrees in there.
But I keep all of my shrimp at room temperature, so in my house that's between 68 and 73 and they love it. I don't use heaters because they take a lot of electricity and shrimp do fine in any range my house stays in, even when the temp drops to 60 when we are out of town.
I've got an outdoor tank too with them
. Breeding flat out stops below 65 in that tank. I don't use heaters in any of my tanks either. But when I did, I had far better breeding out of my neos. I stopped using them because of the power drain too and the fact it was just one more thing to go wrong in the tanks.
And again, I tried to be real clear other folks would have different experiences. I can only comment on experiences I've personally had. Not spouting anything out as the gospel