Joe, I've known people who swear by either or.
I've been using Rep Cal for my box turtles because it's easier for me to buy it.
I have had good results using Rep Cal with the box turtles.
I know people who use Minerall & they have good results. I think either way you go will be ok.

I live in a desert where the soil is extremely high in calcium, I don't feed my tortoise she just grazes on her own. I don't supplement her with calcium at all because I don't need to.
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PHRatz