My complaint is that it doesn't come presoaked so I had to wait before I could use it.
Just kidding of course, the thing is awesome!! I never knew such a mist of CO2 could ever exist. It's better than any glass/ceramic diffuser or even a wooden airstone
I soaked it for about an hour before turning it on and I was in awe. I want to keep my CO2 on just to watch it but that can't happen.
Excellent product, highly recommended!