I changed the water in my 5 gallon Beta tank a few days before the long weekend and I think I killed my snail.
I noticed before we left town the it didn't seem to be moving much but it didn't register as a problem. Now I am confused over what I did to cause this. The following are some ideas and I was hoping for your feed back as well.
I touched the snail for the first time when I changed the water - could that have killed it? I didn't think about about washing my hands before touching it.
I have some goldfish in a pond outside and I may have used the same net in both the pond and the tank - do goldfish carry diseases that could kill a snail?
I had used some "Clear Water" product in the pond out side to remove the cloudiness, it is made by Jungle Labs and I cannot find out what it is made of, I used a drop of it a few days before I cleaned the tank to try and get the water clearer, do you think that is what killed it? It was still alive when I changed the water because I saw it draw up into it's shell - it was only after I changed the water that it stopped moving - could the combination of the drops and the water change kill it? What is the best way to change water for a snail?
When we got home this evening the snail was still in the same place and had sort of "melted" down out of it's shellon to the plant. That was dead right - not laying eggs - right?
I really feel bad and I am now wondering about the Beta I have in the tank - it seems fine but I am worried about disease from having a dead snail in the tank with it for two to three days and if there is some kind of disease in the tank that I need to take care of before it kills the Beta.

I tried to find out what is in "Clear Water." Here is the site on it:
http://www.junglelabs.com/pages/details.asp?item=NJ021
It of course, does not say what is in it! From what they say and a similar product I have at home, I'm guessing it is KMnO4 or potassium permanganate. That IS toxic to snails. The container should say so if that's what it is. See if the paper work that came with it says what the chemical is. If it's KMnO4 the liquid should be pinkish or darker red. What color was it?

Touching the snail gently probably didn't overly harm it. While snails and goldfish can share certain parasites, the chance of something being moved over with the net is very low. Snails are more likely to give something to goldfish as snails seem to be more tolerant of a parasitic load.

Changing water for a snail is just like for fish. Don't change more than 50% at once (except in an emergency), try to add water of similar temperature and water chemistry, leave the snail in the tank if you can during the cleaning, and add dechlorinator if you have city water. Water changes are stressful and may have contributed to the snail's problem. It's rare though that a water change with similar safe water would be deadly.

If the innards of the snail are hanging out and just floating in the current, the snail is dead. On picking it up, if it were still alive, it would hide back into the shell. I'm sorry for your loss.

If the Clear Water killed the snail, the betta should be fine. Bettas sometimes eat snails but I assume you've had them together for a while (and the flesh isn't missing on the snail anyway). What kind of snail was it? I don't think the betta is in danger (but I'm not always right). Good luck!