AST aren't basking species in the wild they are only known to exit the water to lay eggs. UVB is filtered by water so with just these 2 considerations then you can come to the conclusion that its not needed. If you want to add it ofcourse it won't hurt in the wild they would be exposed to stronger levels than most lights can replicate (even do its filtered as it penetrates the water). I'm sure no one would disagree with their use just that its not needed.

Xavier