Goldfish can sometimes be susceptible to many diseases when they are integrated with other fish. Some of these diseases can be infectious as well as transmittable, but other diseases may not be. You may do all you can to take care of your goldfish, but even the best of us experience issues.
If you think your goldfish might be sick, you will want to isolate it from the other fish as soon as possible. You can place the goldfish in a separate container and set it up as you would an aquarium with proper ventilation as well as aerator, but without any gravel or plants in the container.
The container doesn’t have to be very large; it will depend on the size of your goldfish. Separation is important, because, as was mentioned earlier, fish diseases can be infectious and you will need to determine if that is the case with the sick goldfish. This will avoid spreading the disease to any other fish you may. Another reason for separation is because sick or frail goldfish will be attacked or picked on, by the other fish that are healthy.
Goldfish have a reputation of not being very supportive of their kind. Once you have determined the nature of the disease of the sick goldfish you will need to implement treatment such as changing what you are feeding them. Be careful of food with medication in it. You will not be helping the goldfish if you end up giving it too much medicine, so feed and medicate it separately.
The good news is that when goldfish start off healthy they usually stay that way. However, when they do get sick it may be because they were overwhelmed by a bad water system, a quick change in temperature or a change in lighting. It doesn’t have to be one thing, it could be a combination of these issues that could cause sickness.
The bottom line is that these issues don’t agree with the fish and can literally make them sick so make sure you keep their aquarium in proper condition to avoid problems in the future.