Betta's and Neon Tetras

You most certainly can.
But ensure the Neon Tetras are in a fairly good school. This way they will be more social with each other, and leave the betta's long fins alone.
Even though Neon Tetras are not fin nippers, i have heard stories of these fish nipping if they are not in a school.
As long at you have 6+ tetras all should be good.
 
also depends on what size tank you are thinking. It should work out, but if you have a particularly aggressive betta the bright colored neons might be very tempting for him to pick on
 
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