We used a sponge. Oh I rinsed it out and washed it with dish soap and thought everything was clean. Our water cooler didn't get disinfected like it should have. I can't tell you how guilty I feel because of us not knowing everything we lost one of our split to yellow parrotlets and almost lost one of our American Yellow babies. I don't care how much money it cost to find out all of this.
Money is nothing compared to the health of our Parrotlets.
The costly thing was losing our little baby. I cried and cried. So I am going to help all of you to make sure this doesn't happen to any of your parrotlets or other exotic companion birds. The best recommended is bottled water. Tap water has all kinds of chemicals that are not recommended for our birds.