I did not see what size tank? My 200 has 10 Scarlets and 10 Zebra and the tank does fine. I have 5 Scarlets in my Neo Nano and they do a great job. History lesson, I once had a 75 gal., I purchased 2 Scarlets and 12 Zebra. For a year I watched these guys keep my tank clean. Then when Wolf Reef openned, Alex sold blue legs cheap so I bought 6. In six months I was down to 2 blue legs and 1 Scarlet.