Goldfish illness can be an awful thing to discover, as we usually have little notice before they give up and die. Keeping your goldfish in an unfiltered bowl can cause a few more types of goldfish illness than with a filtered tank, as bacteria and fungus tend to build up eventually, no matter how well or how often you change their water. Goldfish are pretty hardy, but they are still one of the more delicate and mysterious animals that we choose to keep, so having preventative measures and a bit of information on hand before purchasing your fish can be of great help to both of you in the future. Cloudy water means that there is a greater risk for goldfish illness to present itself, so watch closely and be ready to help.