Why can't I grow coral?

[hrdneglcry]

I made the mistake of treating my system with Epsom Salt. It was for a fish that became blocked. Since that time all of my coral has died, and no new coral will grow. Or very little as something is growing in a few rocks but gsp becomes brittle and just flakes away. The H20 has been changed at least 3 times for the entire tank volume. Much had to be changed because after adding Epsom the refractometer said the salt was so high I had to change so very much to get it back to normal.
The fish have not died. The crabs are all alive. This has been ongoing for 6 months or more. I bought a gsp frag to test it. It will not open. The tank was full of gsp and it all died. Even the pink mat just crumbled.

 

[Reeftanker]

I'm no expert, but, i would be doing weekly to bi weekly water changes to dilute what you put in the tank along with carbon in the filter chamber.
Check all the parameters and make sure they are in range.

 

[griss]

Yes, what are your current water parameters. Epsom salts (Magnesium Sulfate) are one of the ingredients in Mg supplements so, I'd be curious to know what your Mg levels are. If you can test for Sulfates, that might be a tell as well.

 

[Reefing102]

Not exactly a best answer, but I might run an ICP test. My incredibly limited understanding of chemistry interactions and reading info from @Randy Holmes-Farley indicates that sulfur depletes alkalinity as well as a possibility of elevated Mg from the Epsom. That said, when you did your water changes, were they 100% changes each time or several small water changes over time? Several small may not have diluted everything sufficiently. Just thinking outloud