I'm a long-time planted tank keeper. I always do a 30% water change weekly, but this week let it go 6 days extra due to busy schedule, etc. It looks like my mature Angel is just getting started with ich...about 11 white spots - no one else has it yet. Can ich spontaneously occur without adding new fish/plants as carriers? I've only treated for ich once, years ago, after adding 5 new Rummies. I am puzzled!