kboese I know and feel your pain! mine is doing the same thing, you might've seen the other post I started when I didn't know you created this one.
Anyway, we don't have PETco's here, just PETsMART's - they have those spill-less bowls on the website but not in any of the local stores. Not glad you got one and didn't work, but it does save me $20. from buying one and paying half just for the shipping because I think my kitty will just knock over that one too.
What I've tried:
changing water level low & high
changing bowls, big & small
I change the water twice a day, once in morning and again at night
= nothing worked so far, she just seems to have to tip out some water for fun I guess and she's got A LOT of toys to keep her busy.
One thing I have thought of, I've read that cats are not color blind, but do see some colors better than others with some looking just gray... so I think I'm going to try different color bowls - maybe she's interested because the water is so clear and appears to just float so they have to play and figure it out. If that doesn't work then guess I'll just bolt or nail a water dish to my floor!
Some posted this or a link to:
"From the research I've done, I found that most experts on this subject do believe cats see in color. Cats seem to respond to the colors purple, blue, green, and yellow with blue and green being the strongest colors they perceive. Red, orange, and brown colors appear to fall outside a cat's color range and are believed to be seen as shades of gray or purple."
Good luck with yours and let's both post if and when we find a solution to ours...!