I had a huge green carpet. when fully opened it was the size of a dinner plate. it ate 3 of my fishes and killed a bunch of zoo's. i really liked it, but in the end..i traded it for some more zoo's/hammer/and button polyps. i usually fed it silver sides....sometimes it would spit them out after a while...thus leading to my nitrates rising. if u have a very large tank..i guess it would be ok...