That sounds nice and cold.
>> But then I'd have to open the container to give it water, right?
If it's pretty tightly sealed, it won't evaporate very fast. Maybe check every few weeks, at a guess?
If you have vent holes, maybe spray some mist in those every few weeks, and open to check every 4-6 weeks??
I shouldn;t even make suggestions about WS until I have something more like success with it!