I had this large and healthy Turquoise for 2 years. He was a male and he was very vigorous. He used to dominate a smaller Australian Rainbow. The Australian Rainbow stopped growing so I moved it to a larger tank. Now, the Turquoise was a little too large for the 10 Gallon tank. So, I moved it to the 30 gallon. Immediately, the Turquoise rainbow was attacked by the smaller Australian Rainbow and a giant danio. The second day, the Turquoise did not look okay. so I isolated the Australian Rainbow and the giant danio. Still, the Turquoise male died in day 3 in a very rapid process. One minute ago, he was fine and eating. A minute later, he could not breath and died. This happened to me before. Are Turquoise vulnerable to bullying?