you have to watch what you start dumping in your tank many inverts are sensitive to chemicals. As far as age goes I was 10 and doing water changes and adding declor and had fish breeding. I had no help and my fish were always fine. No offense but this waving arms to scare fish sound very immature. You either like the hobby or not everyone loses fish from time to time but they don't quit the hobby unless they don't really enjoy it to begin with.