I have a neon tetra that has developed a large belly over the last few weeks. Now it has a large encapsulated sac exiting from the bottom of the fish. The infected fish is also staying close to the bottom of the tank. I have had these fish for several months now without any problems. Not sure what to do. Any suggestions? Also will the other fish in the tank be infected?

I don't know the specifics of tetra breeding enough to know if this is just a female tetra about to lay eggs or if its really a sick fish. Tetras lay eggs as opposed to live bearers. I would at least be testing the water to see if any chemistry is off, maybe add a pinch of aquarium salt for good measure (read the directions on it for your tank size) and watch closely. If the fish returns to normal looking then you may be having tetra babies (called "fry") if you have a male to spray the eggs. In the 55 gallon aquarium I have, they'd sadly be eaten before I ever saw one. Good luck!

I had fresh water fish incl many tetras over the years - I think your neon is on the way out, rather than getting ready to lay eggs.
If you can, quarantine the fish in an empty tank/jar/somewhere else for the next day or two to see if its going to make it or not.

Best of luck - you can call your local fish store for advice as well...