hello, i'm new here with goldfish. i recently set up a 30 gal. hex for my wife, she loves goldfish. after the tank was cycled with filter media from another established tank, we added three small ryukins on dec. 28, 2006. they were all doing fine, eating and swimming all around until this sunday when one of them was listless on the bottom. water parameters were all fine. the one finally died on monday. any ideas?