I use a 2 gallon heated bucket for my silkies. BUT I do not have it in my coop or near it! It's in the corner of their run, I really didn't want to go the heated bucket route, nor did I want to be kicking frozen blocks of ice out my buckets, in 10 degree mornings... so heated buckets it is! 

Mine is similar to the one below!
https://www.ruralking.com/farm-inno...j5Eh6_z5df7RwKze68W9SvsAQxSRZMYRoCzfEQAvD_BwE


Mine is similar to the one below!
https://www.ruralking.com/farm-inno...j5Eh6_z5df7RwKze68W9SvsAQxSRZMYRoCzfEQAvD_BwE