Let me clarify something...
I've read the posts on this thread and feel like you guys/gals need some clarifications.
#1-Fish that are born with bent spines mostly get them from poor genetics and all the in-breeding that has been done to create these different color strains. There's nothing you can do for these fish that will remedy the bent spine. These fish are not "contagious" as per diseases and are not a threat to your other fish except if they live long enough to breed. This genetic "fault" should really not be perpetuated as it is a hardship on the fish to some degree. The choice obviously is yours but my opinion is to try to maintain a fish's shape that closely resembles it's wild ancestors as much as possible. (I know that comment is going to get a big retort but I'm entitled to my opinion too
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#2-Fish that develope a spinal disfigurement over time, usually have a vitamin deficiency which means that you are not feeding the fish correctly with the proper foods. This is a preventable condition and in some cases, when caught early enough, can be remedied with the fish returning to "normal."
Both of these situations unfortunately look similar in the end but shouldn't be confused. You can easily determine their origin by knowing what they looked like when you purchased them or if they started out this way upon birth.
To remedy situation #1- you need to add new bloodlines into the strain to help bolster the DNA. This new fish should NOT be from the same family (i.e. a different sibling) but a more natural looking member of the same specie/family. Do some research on genetics and you'll see how to add good internal genes while showing the external characteristics you are looking for.
To prevent situation #2- if you are only feeding a prepared diet or one type of food only, you should be adding additional vitamins to the water after your weekly water change. This can help prevent the condition. Livebearers often have multiple babies that are disfigured. In nature, they would most likely become food for the healthier fish. (Circle of life stuff.) Controlled, selective breeding will help prevent or delay these disfigurements from taking over.
I hope this clears things up a bit for you all