Dunk tank and dropping temperature problems

[mykl]

I keep a thirty gallon pail for watering my orchids - especially the vandas.
It has proven quite successful all summer, but now that the temperatures are starting to drop, I'm concerned how long I can continue this practice into the winter.
Being a fairly large volume, the water can't cool all that much on any given day, and in zone 9B I don't expect very many days of frost/ freeze.

At what point would the temperature cause the plants to shock?
THNX

[Roberta]

Consider a little aquarium heater. My plants get watered in the morning from a 55 gallon drum that my RO unit refills during the course of the day, so it has all night to cool before hitting the plants in the AM. I have the aquarium heater set to keep the water at 68 deg. F (20 deg C), the lowest setting. (In my case, since I'm drawing down the water level and don't want the heater to every be dry, so I have it on a timer plug that runs the heater only at night, nothing special camr from Home Depot)

[mykl]

That was what I had in mind, and giving me a temperature target is greatly appreciated.

[Roberta]

Aquarium heaters are rated based on volume. So for just "taking the edge off" the cold, on a small volume, a very small heater will do the job, and not draw much power.