Some people's rabbits love frozen water bottles. Mine on the other hand don't touch them...
Definitely clean that out. It could be the start of vent disease, which can be a big, gross problem.
I only have one doe that doesn't like the frozen bottles, she'll shove it into a corner and leave it there to go back to her tiles CD... Okay I'll do that right away, is there anything specifically I should use to clean it or put on it aftawards as a preventative?.... Nothings ever a deal is it