I went and put the 3 smaller Koi into the extra 10 gallon tank. They are only about 4 inchs long. I hope this will reduce the cloudiness that keeps happening. The other 4 that are about 8 inchs are still in the 55 gallon tank. I am also vaccuming the rocks every day. So I hope that helps. SUggestions are welcome. I am learning as I go.