Please Help with my snails and corals

[kenman999]

I placed a poly pad in my filter for a week now. There is no colour change on it at all. No copper or heavy metals i suppose?

One of my friend told me that I don't need a canister filter in a reef tank. Should I remove mine?

I brought my water to a lfs again this week and it showed that my mg is 600. She checked it twice with two different test kit(elso and something else) but my cal and ak level r both steady. 420 and 8kh. I have added mag in hoping to bring it back up. My phosphate-0, copper-0, all other readings r perfect.

All snails and corals r dying in my tank in one/two days. What else can I do now. If there r something so toxic that can kill em in 2 days, why r my shrimps, fishes and hermit crabs doing so well?

Please help.