I was looking for a grazing source for my 10 gallon Caridina shrimp tank and stumbled across the Kallax ball. It was exactly what I was looking for and my shrimp have been all over it since I dropped it in!
I used both the Lubao and Kallax and they are very good. Be sure to soak before use for 3-5 days and change the water daily. I kept it in a little feeding dish inside the tank and biofilm will start growing quickly. They last about 2 months so keep that in mind but overall, I am very happy with them.