I use carbonated water for my Marimo ball It had a couple small light brown spots on it when i bought it. someone recommended I give it a carbonated water dip every now and then to help the brown spots go away. I have a soda stream so I just made a little carbonated water put it in a cup and let the marimo ball float in it for a little while. Then I put the ball back in the fish tank. Im not sure how it would work putting the carbonated water in the tank. I was afraid to put the carbonated water right in the tank because I have fish so I wasn't sure how much would be OK for the fish.