If it makes you feel any better, I made a similar mistake when I was first starting out. I didn't properly cycle my new tank and lost a bunch of my fish. My jack dempsey, which I still own, was however hardy enough to survive the ordeal. I'm not saying it's a guarantee that yours will be OK too but they're tough fish, good luck! And the best advice you can get for fish keeping is on this forum- rarely have I received good advice from petco.