5.5 lbs. luckily. She has stopped trying to open the lids. Few squirts of lemon juice when she did and she has decided that it isn't in her best interest. She still is trying to go behind the tank to get a closer look at Snake, the dojo loach. She likes that when she gets close, he freaks out and takes off at breakneck speed through the tank.
Also, she has become fascinated with the 55 gal. since we added that cichlids. She sits on the kitchen table staring with longing. That's one I know for sure she can't knock over though.