Anyone have luck with cardinal tetras?

Well, I replaced the cardinals today. Let's see if these guys fare any better...
I only did a 30% water change before adding them (I was advised that it would be good to have some of the meds still in the water as a preventative measure...I hope this was good advice). These guys arrived at the LFS a week ago, so I imagine they are the heartiest of the original shipment. I was also told that these were not wild caught. I thought I had read that most cardinals in stores today are wild caught, and that is why they are so fragile. Anyone have any insight?
 
Yes from reading I have heard many times that whether neons or cardinals the wild ones are much less hardier then the tank bred ones.
 
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