None of my fancy goldfish have it, but I want to be aware of the symptoms. also, what can you do to stop it? I've heard feeding it peas and medicated food, but is that it? Thanks!

swim bladder problems are actually a couple of different things that all result in the fish being unable to keep himself rightside up without effort.

Feeding:
usually it's because of overfeeding or feeding too large a pelleted food, or too much of a meaty food like bloodworms.
some people feed shelled/skinned peas, either thawed from frozen or slightly cooked if from raw.
frozen brine shrimp or mysis shrimp can also be ok treat foods as long as not overfed
If you don't feed for two or three days the symptoms should go away or get better

Water Quality:
a variety of things can cause bad water quality or stress to the fish which may lead to the same symptoms.
too many to list, but the most common are
temperature shock, like what happens when you take the fish out to clean the tank or something ridiculous like that.
cold tank
high waste levels or high bacterial levels, from either overfeeding or from overcleaning the filter

Genetic Defect:
can't do too much about this, except feed properly, keep tank above 74 degrees F, maintain good aquarium cleaning and maintenance practices, and don't over feed. Fish with this defect can live healthy lives unless they are fed badly and an infection sets in.

Internal Infection:
usually caused by one or more of the above, no treatment is effective until the above items are correct, and often will clear up if you have corrected the cause. in extreme cases, an antibacterial food is the best treatment.

The fish will be floating upside down in the water if they have swim bladder probs. I don't know how to cure it though….sorry.

what Kim said but here is a website to help you also.