Hi! I'm new here and I signed up because I'm having an issue with a new fish. I have a 75 gallon freshwater tank that had an Oscar and a Jack Dempsey. They lived in peaceful harmony and, knowing that our Jack was a female, we decided to take in another Jack Dempsey as a rescue, also a female. We went through proper quarantine procedures with the new Jack, and the only issue with her was that she has a popeye. The previous owners said she got it after a power outage 2 years ago. So, we introduced her to the tank after a 2 week period. The two Jacks seemed to bond and enjoy eachothers company, but the Oscar bullied his new tank mate. She retaliated and Oscar got a nasty bite on his face. We ended up moving the Jacks into a different tank. Oscar contracted what appeared to be a fungus infection and despite our best efforts, he died. Shortly after he died, the other Jack also seemed to contract the same fungus infection and died just as quickly. Even our foot long king pleco died from this same disease. I assure you, we made every attempt to save these fish. It was a heart-wrenching experience for me. Through all this, the new Jack seemed just fine! No signs of infection at all. We quarantined her again for a week and introduced 3 small goldfish as an experiment, and sure enough, all the goldfish are coming down with the same exact infection. So, to my question, is it possible for a fish to carry a disease without contracting it?