have a problem with some corals

[shavo]

OK i did a big change this week on my tank and also did a 20 gallon water change in the process. I also pulled out all of my crushed coral and added a dsb. Since that my orange cap montipora has completely turned from a brilliant orange to white in 2 days. I think it is dead. I tested my water perameters and everything is in check. I only added about 20 gallons in the process on a 125 gallon tank. It was one of my favorite pieces and now I think it is gone.
Ias i said I checked everything with my test kits and can't find anything out of the ordinary. The only change is from crushed coral to reef sand.

anybody have any thoughts as to why?
I also had a green cap that did the same thing, both are white
other inhabitants (corals, fish, and inverts) all appear to be completely normal and doing great, just the two hard corals took a hit. any advice or insight?

 

[mr_X]

check on the manufacturer of that sand..did you save the bags? research that first. headed to that fish place today chris, come out here and we'll go up together. KOP mall.

 

[dnorton1978]

That is not by chance a residue from the sand is it? I am sure you tried to blow it off, but if not give it a try..

 

[ChrisRD]

Sounds like they may have bleached. Changing out sandbeds like that is a major upset to the system. Major changes like that will often bring a negative reaction from the more sensitive corals IME. Things should settled down now, but it can be tough to get a stony coral back from the brink if it has bleached.

 

[Anonymous]

What ChrisRD said.

 

[EEric]

I had my chiller break down this summer and almost all my stuff bleached, but most came back.My orange cap turned pure white ,it took about 3 months and it's back fully.
My other cap only came back in spots ,I'm going to frag it out soon .Maybe you might want a piece.

Here's a pic before.