Very fat fish.

Question
I have a thirty gallon tank that was given to me about 9 months ago. All has been going very well the fish apear to be healthy and active. About 3 or 4 weeks ago one of the small orange fish started to become VERY fat and seems as if it might explode. It continues to be active and seems to eat well. I'm worried if it has some illness it might affect the rest of the tank. What is it? What if anything should I do?  Thank you for your quick answer.
Beth

Answer
Dear Beth,
There are many triggers that cause bloating in fish. It could be dropsy,constipation, or gravidness (being pregnant). *I can give a more thorough answer if you could please tell me what species the little orange fish is.
Thank you.

Eating well and remaining active are good signs your little orange fish is probably not sick. ;-)

Best wishes,
Karen~