Abbiesaurus, sometimes fish just put their fins close to their bodies for a short moment, and then usually not all of them. But you'll notice if a fish is uncomfortable, if they stop somewhere and put their fins together that's usually when you should worry a bit. They only move when they notice food or something
But if the fish is generally acting healthy and the water's fine... it's alright. You may want to be extra watchful for a while though, just to be safe.
Jack: It's very hard to over aerate your water, and it's close to impossible with goldfish. The concentration of oxygen in water is surprisingly low, even in the best aerated environments. And so, that's pretty much nothing to worry about
It can happen that some fish may develop small air bubbles on their fins and skin (INSIDE, note that small bubbles sometimes just stick to the surface of the fish without being symptoms of disease), which is in turn a symptom that shows over-oxygenation. But really, when it comes to goldies, the more air stones/filtration the better
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