I would never buy from a pet store. They may be eating, however there may be other problems. If you watch it eat, then it's a step in the right direction, but i'd want to see eat/defeciation/shed records from the snake. Especially a snake as high end as a Chondro should have records on it. If they don't, that would red flag it for me.
But as I said, one meal is not as much of an insurance policy as you may think. You may get it home and can never get it to eat again. I would make sure it has at least 10-15 meals, documented on paper, in it before I brought it home. Most breeders wont let their Chondros go before they have had this many.
As Greg Maxwell puts it "You are not shopping for the right animal nearly as much as you are looking for the right breeder!" I honestly have to say better words haven't been spoken.
Personally, I don't buy anything from pet shops except for caging supplies. Reason is that usually in pet shops you'll end up with a lot of highschool kids who just want some money to go get drunk on the weekend, they don't know how to care for the animal, and so they won't. I know of one pet store I used to actually work at that only would feed their neonate snakes every other week! When I questioned this, I was told "well they rarely die from this." That, along with a lot of other things, caused me to quit and turn them in to the feds, but thats another story.
You can also get snakes from pet stores that have parasites, mites, etc. if you DO decide, for some reason or another, to buy a snake from a pet store, quarantine it in another room for at least 6 months to make sure it's free from parasites/mites...this will help prevent spreading to the rest of your collection. (Really I quarantine all my new snakes for 6 months, no matter where I get them. I'm obsessed about that.)
If you do decide to get one from a pet store, quiz them. Quiz on feedings, care, husbandry, etc. Ask to see their back room. Some back rooms are absoutely filthy. Some are nice. It's just the luck of the draw.
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-Chris
0.1 Licorice Stick Black Rat
1.0 Black Rat
0.1 Vietnamese Blue Beauty
1.0 Green Tree Python
0.1 Texas Bairds Rat
The educated are the few. The uneducated are the masses.
North American Rat / Corn Snake Care Sheet