Box Turtle white marks - should I be concerned or residue from coconut oil?

[johnbell670]

Hi Forum!

I have noticed recently that my box turtle (Deuce) has some white residue prominently on the side of his shell. I've been applying coconut oil weekly for preventative care for around 6 months, but didn't notice this until recently. Does anyone know if this is just residue from the coconut oit, or if it's something else I should be concerned about? (Pic below, you can see the white on his side)

 

[Markw84]

looks more like hard water stains - calcium/mineral build up. Are you using municipal hard water to bathe and spray your tortoise?

 

[johnbell670]

looks more like hard water stains - calcium/mineral build up. Are you using municipal hard water to bathe and spray your tortoise?

Thanks Mark. I am using filtered water for bathe and spray from the fridge. If this is calcium buildup, any recommendations on a better water source, or treatment?