Plain water works just as well but obviously not in a cold winter climate. I have used this method in our basement at times with great results. However, it really doesn't work to well when it freezes. On a side note, a mouse will likely have great difficulty climbing out of a 5 gal bucket even with no liquid at all and that is the safest for your pets in case they are exposed to the bucket. Also, this way the people who are against the 'unethical treatment of animals', i.e. rats, may dispose of them by simply transplanting them across town......