Copper & lime question

Anyone have at their fingertips what a dangerous level of copper is? If my
tank measures copper at .15 ppm is this too high or about right?

Also, I know that snails build their shells from calcium. I know someone
who drops dolomite tablets into his tanks. He says this keeps his KH up
nicely and that the snails eat it for their shells. Will dolomite do the
same thing as Calcium Carbonate? I think of it as lime, such as dolomite
lime that one adds to the lawn. I usually grind CC up and add it to my tank
that way. Maybe I should drop a tablet in for my snails?! Anyone else out
there use lime in their tank?

in Vancouver with mostly sun, a few clouds.