I've spent so much money on those things and I think I'm actually only using one. What I didn't think about when I bought them is, they are sharp! You know how most of them come with a hole in the middle? Once I had a goldie who was sick and actually dying, but for some reason she got stuck inside the hole and I had to pop her out! When she came out of the hole, a bunch of scales came flying off, like metallic rain. Also, you can't use them with bettas because they snag the fins, I can't use them with my african dwarf frogs because they have such sensitive skin and I'm afraid to use them with my bristlenose plecos because I'm afraid they will hurt their mouths.