Let me save you the money I've wasted.
Over the years I've tried every kind of cat fountain in my practice. The cheap ones off Amazon, the plastic ones, the ceramic ones, the ones with the app. Six of them I wouldn't put in front of a cat again.
The seventh was 304 medical-grade stainless steel. Non-porous, so there's nothing for biofilm to grip. It's the only one still on my counter.
Here are 7 reasons why this stainless steel fountain is the only one I recommend now
