carbon with phosphate

I saw this on another website. Is this true, is it a way to check if carbon has phosphates in it?

" Make sure your activated carbon is not leaching phosphate into the aquarium. You can test this by testing the aquarium water for phosphates and then dropping pellets of your activated carbon in the test tube. If it leaves blue trails as it drops to the bottom, it is leaching phosphate and should not be used in the reef!"

This page also says not to use distilled water, but how is distilled water any different than filtered?

"Absolutely use filtered water: either R/O or de-ionized, (but NOT distilled) water for your top off water! Do not use distilled water since it may kill an entire reef. Because distilled water has lost all of its minerals and anything else it might have, the water molecules will bond with the fish/invertebrates that have these minerals that were lost by the water. "

What are your insights on this?