Acros melting away. Suggestions? (picture)

[maury]

Hi all, long time no post here! I have had a sudden change in my tank, and hence the reason for my return!
About 3 days ago, I noticed two separate acropora colonies just start to bleach/melt away. The tank has been up for about 7 months, and had been stable as a rock (coral wise) About 3 days ago, the bleaching started rather rapidly, decimating a larger, purple colony, which I have removed. This green colony, is a rapidly growing frag, from friends tank, and is a very hardy coral. There are three other acro colonies in the tank that look great. I know that bleaching in acros is a sign of stress, but for the life of me, I cannot figure out what. There have been no new coral additions in the past month; the water parameters have been very stable, except for a slow drop in Calcium from 450 to 380, due to maladjustment on the calcium reactor. When I first noticed the bleaching, I did a 25% water change. Hasn't helped.
Now, I did not think a dip to just 380 would do the acro's any harm, not to this degree. Just slow the growth rate a bit. The rest of the parameters are as follows:
Tank: 210 gallon with 75 gallon sump, 300 pounds LR with 4 in DSB
Temp: Constant between 79 and 81.5 (maintained with chiller/heaters)
Ph 7.9-8.2
Am/N/N 0/0/0
Silicates/Phosphates: undetectable
Lighting: 3, 250W 6500K MH, 6 months old, plus 4 160W vho tubes, also 6 months old
Any suggestions?
Pic attached

 

[10k]

Doesn't look like bleaching to me. Looks like tissue recession...BAD ...VERY BAD. I had a bout with this, and lost several Acros before it just quit...I think. Could be because of the Calcium drop, or Alk problems, or Magnesium deffeciency, or low Strontium levels. You need to do more testing to find out the culprit. My problem was Magnesium, best I can figure. It was low, and recession stopped when I got it back up to an acceptable level.
I wish you all the luck in the world. I feel your pain...really I do.
Also, as Sammy pointed out, I see Cyno on the skeletons too. Could be just taking advantage of a free meal, but it's on the live rock too. Check out your Phosphates. Probably high

 

[j21kickster]

Looks like RTD- rapid tissue degeneration.( quick tissue death from the buttom up) There isnt much known about it, but studies are being conducted as we speak. It is suggested to be caused by an outside pathogen and most ofetn occurs when the coral is stressed. It is most common among acropora corals, it can happen over a few hour or a few days (but eitherway it is a quick process) there is not 100% cure but it should be removed from the tank so that it wouldnt spread to other corals (mainly your acros) Some reports have shown that dailt dips in Lugols solution has stopped the degeneration- Also you can break off the parts where the coral is dying then dip- this would also help the tissue degeneration from spreading. It usually kills corals but if you do something soon - it could survive. The dips mainly kill bacteria living on the rotting skin and help ease stress- So the dip doesnt work directly but instead has beneficial side effects. HTH

 

[bang guy]

Time to frag the heck out of it so you don't lose it all. Don't be stingy with the cuts. make sure there's some flesh between the tissue recession and the frag.
How old is your Nitrate test? I'd get a second opinion. Just a gut feeling.

 

[maury]

OK, to update on some of the replies
First, thank you all for the fast, and knowledgeable replies. I used to get a few off the cuff responses quickly to my questions from folks that don't really know the hobby. All that have replied obviously do!
Secondly, I made the picture smaller!
Yes, you are all correct, I should have been clearer. This is NOT a bleaching problem; the coral is dying, and receding very rapidly.
I have not tested for any trace elements, but I do have a strontium and Mag kits (Salifert, <8 months old (purchased at least)) will test these, but aren’t these elements also being supplied via a calcium reactor as well? I know Strontium is. Anyway, I do does with reef plus (the only additive I use outside of DT's), however, I have not measured these levels (might be high!) I will do.
The bubbles. This is not cyano, it's dinoflagellates, that I have waged an on again, off again battle with for 6 months. They come and go, but never really bad, and they were not on any of the corals, so 'smothering' from dino's would not be an issue. I know all about the food sources of dino's and what to do to kill/reduce them, and for the live of me, I don't see where they get an organics load in my tank, which only has 6 small fish in 300 gallons of circulating volume! I feed once a day, and with small portions, nothing gets left. I also run Ozone (safe, zero residual in return water, run with Aquacontroller 2 with thermostatic control via the ORP probe) so I am cooking the organics away! Also cooking the 'good stuff' as well, but that's why I use DT's to feed the clams and sun coral.
Another question. If this is this rapid tissue regression mentioned above, is it something that may spread? If so, I'll rip that whole acro that is receding out as well, hate to lose the pretty blue and red colonies that are in there. I can easily replace this green one from my buddy's tank, as the mother colony is 3 feet across and grows like a weed.
Thanks again for the quick responses, and I'll get to testing those trace elements!

 

[maury]

Oh, and the nitrate/trite, amm kits are all fairly new Salifert kits, plus I triple tested the the Nitrate with a 'doc wellfish' kit (don't ask) as well as a tetra kit. All read zero.

 

[j21kickster]

If it is RTD, and im pretty sure it is, yes it can get to your other colonies- do you have a qt tank? If not i would take it out- frag it, dip it, and hope for the best

 

[maury]

The clam has been there two months, and he opens larger. And the dino load in the tank is VERY small compared to what it was, say 4 months ago, and these acros have been in there when the dinos were in LAYERS on the sandbed, so I don't think it's them, I think it has to do with what's stated below.
OK, tested the Mag and Strontium. Guess what? The mag is low, at 900 ppm, and the Strontium is at zero! I will be picking up an additive tomorrow, as I went back and read the content of Seachem Reef Plus, and no Mag or Strontium. Thanks for the tips!

 

[10k]

Sounds like you found it. Good for you/us! Just remember, bring them up slowly. Maybe a little faster than normal, but don't overdo it, you'll be helping thier demise...

 

[blondenaso1]

Sammy, why do you say get the strontium without the Molybdenum? Just curious because I use the Kent Str/Mol supplement.

 

[josh]

Sorry for your losses......RTN is a son of a gun. I just lost a pedestal table yesterday. It wasn't RTN, just progressive bleaching, I fragged the heck out of it to no avail.
I don't have much to add that the others haven't covered, I might suggest target feeding what's left of it after you frag it. Although I would just remove b/c as mentioned RTN can migrate from coral to coral and wipe out all the sps. Do some water changes and aggresively run carbon.
Good luck,
Josh