I have the same problem with my new girl. No matter what, it is her job in life to imediatly knock over the water when she sees that I have replaced it - After having a sip, of course. XD

My suggestion would to either leave it, or to slowly add more holes to the tub. Maybe start where it is more aesthetically pleasing. With my girlfriends spider, I put four holes on the lid and it solved the problem.

Also, if you don't like melting the holes, I use an exact-o type blade and it works great. It takes a bit of practice to get them nice looking, if the blade is dull (like mine is). Just apply pressure and spin.

Hope that helps slightly.

Pita