Rapid tissue death - any help?

[John Stuckey]

I have a Biocube 29 that is heavily stocked with fish and corals. The tank is about 18 months old and everything was running smoothly with the exception of mild green hair algae due to elevated nitrates and phosphates.

I had a gold and black damselfish that had started to go mean. I decided to remove him and take him back to the LFS but couldn't catch him. I ended up removing the rock to get to him out. After removing him I put the rockscape back together. In the process I completely moved all of the sandbed around (about 2-3 inches deep).

Within 2 days, I began to see significant tissue death on an encrusting favia that had been extremely healthy for months. My others corals were doing fine. I have a nice 3"x3" chalice that looked great. 2 days later I woke up to see major tissue loss on this chalice - literally overnight.

I checked parameters. For reference I use Red Sea Coral Pro and change out 5 gallons every weekend.
Alkalinity was at 6.3dkh (normally 10)
Calcium was 350 (normally 390)
Magnesium was 1300
Phosphates .49
Temp 79
Salinity 1.025

I immediately started dosing Red Sea A, B, C (separate liquids) using the minimum daily dosage recommendations for 20 gallons. After 6 days my Alk was back to 8.8dkh but calcium and magnesium dropped to 290 and 1240. Two more hearty favias started breaking down. Fish, softies and euphillia are showing no problems, nor is one of my other small chalices. But the 4 affected corals are dying very quickly.

I decided to do a major water change using just mixed water (I got concerned that my previous practice of making and storing saltwater was degrading it). I changed out 8 gallons at once yesterday.

Not sure if it has stabilized or not yet. I'm watching.

I have several possible culprits for my problem.

1. Major disturbance of the sand bed released something that impacted the water chemistry.
2. My dosing (chasing parameters) caused problems (but what parameters cause rapid tissue death?)

Other changes recently. Switched out CoralLife skimmer for AquaticLife 115, dosed (maybe overdosed) AlgaeFix - but this was a few weeks ago and my problems occurred almost overnight. I believe the overdose killed off ALL my microfauna by the way - something did. New Phosguard, new Chemipure Elite.

What might be causing this tissue death?

Thanks!

 

[CodyRVA]

Following. Had a similar issue which I believe was the result of a high nutrient spike, although many others disputed that was my issue. I'd imagine you're on the right track with 1 & 2.

 

[Alfrareef]

Have you tested for NO3?

 

[Diesel]

This is a result from rapid change in parameters.
You turned the whole tank upside down, dosing, large water change.
Basically a fast change in parameters can turn out for the worse, by moving around a 18 month settle sand bed in it's whole is almost asking for a total crash.
Better was cause you just have a 29 gallon is that when all rocks were out you removed the sand and all water, rinsed it good and put it back with new water with the right parameters.
In that cause you just went through a mini cycle as all your rock are still 100% with bacteria and it would have cycled fast.
Or............. next time you just leave your sand bed as it is, don't disturb it, rocks and coral back, 25% water change and good to go.