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Discussion Starter · #1 ·
I have an acro that i purchased 3 weeks ago. When i bought it I superglued it to a rock so that it would stand upright. Its been doing great with full polyp extension but i am noticing the base has started to bleach. My water parameters are as follows:

Ca 460
Dkh 12.0
SG 1.025
temp 80 degrees
Mg (high at 1600)
Phosphates .06

Also, I am running a calcium reactor beginning this past week and my Ph is generally between 7.76 and 7.93. I am all dialied in and my Ca and Dkh levels have been constant.

I have not seen any red bugs or AEFWs. . Even where the base is bleaching, I still see full polyp extension. Need advice. I have done water changes but my Mg has not yet come down. I am hoping it will over time. Everything else in my tank is thriving. A picture is attached. Its not the best but you can see that all around the base there is white bleaching. Could this be the result of the superglue touching the living tissue? If you look at my avatar picture you can see the placement of this coral. Its the tall one on the upper left side of the tank.
 

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Aquatic Philosopher
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My guess... acro eating crab and they do not always hid on the colony either. .
 

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Discussion Starter · #3 ·
There is a white crab living in the acro.... I was under the impression that these are reef safe i have two that i have seen in my tank. So I should remove them? The one living on this coral is white and I have an orange/white one living on my green stylo. Both are smooth..... not hairy. based on this description are the Acro Eating Crabs? I haven't seen any hairy crabs in my tank. I have 3 emeralds and a ruby crab... same as my emerald but reddish. I also have 2 porcellian crabs and a bunch of blue legs and red leg hermits. If you conclude that these acro crabs are the bad kind, how do I get them off of the coral? I have never seen it on the base. The smooth white crab is always in the middle of the coral.

This is a picture of the type of crabs i am seeing http://www.google.com/imgres?imgurl=http://www.utahreefs.com/forum/uploads/jfinch/2004-10-03_164532_acrodamage.jpg&imgrefurl=http://www.utahreefs.com/forum/forum_posts.asp?TID%3D3841%26title%3Dacro-eating-crab&h=480&w=640&sz=90&tbnid=exQCxL-7Fh3RdM:&tbnh=91&tbnw=121&zoom=1&usg=__uotgvxK0VsJXQb9rqb7izcyb_0E=&docid=zhj3PKTSh0YbsM&sa=X&ei=TcOnUZqIDsno0wHd64HgDA&ved=0CEYQ9QEwBA&dur=1551
 

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Double check the ID of the crab to make sure it is not an imposter. Watch the other crabs closely to see if they are the culprits, unlikely to be the coral crabs.

Coral crabs are known to eat the mucus of the coral it inhabits and will also eat dead or dying polyps. But, if the coral is a good size, the amount of polyps it eats won't have any affect on the coral, in fact corals in the wild are known to have a better chance of living w/coral crabs, then w/out them. I don't think the coral crab is causing the issue of bleaching, if in fact it is a bleaching event that is happening.

A article on crabs. It does cover the acro crabs, but also covers all the other crabs which are not 100% reef safe: http://www.advancedaquarist.com/2010/12/inverts

An interesting 2006 study on coral crabs: http://news.mongabay.com/2006/1023-ucsb.html

Here is a list of coral crabs to make sure that yours has the right ID and is not an imposter: http://www.chucksaddiction.com/coral_crabs.html
 

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Discussion Starter · #6 ·
Based on this I clearly have coral crabs that should be ok. The polyps look fine other than the bleaching of the tissue... I don't see any RTN or STN. Any recommendations on what I should do to try to reverse this bleaching, or just sit back and let nature take its course? I have a ruby crab that I have seen often toward the top of my tank but I have never seen him picking at any corals.
 

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I am not very helpful w/the whole coral bleaching part of things. I have also lost sps randomly (it seems) with bleaching. All I can point to is that the coral doesn't like the change in Mg levels. Hopefully you can get the values down to normal levels and the coral can recover. I have had some coral recover (regain zooxanthellae) and others that didn't. I've never attempted to have acropora corals b/c of how sensitive they are. I hope other members will provide more info on that subject (who are more experienced).
 

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I've lost a few sps corals from bleaching at the stem this past year as well, and so have done much reading on it, even though I really hadn't determined the reason why. I found this website of links to have the most comprehensive list to help to figure out what might be going on: Coral Diseases and Parasites

One last link, older article, but found it also useful, "Old Tank Syndrome", does it really exist?: Feature Article: Old Tank Syndrome - Advanced Aquarist | Aquarist Magazine and Blog

Good Luck
 

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Aquatic Philosopher
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I've lost a few sps corals from bleaching at the stem this past year as well, and so have done much reading on it, even though I really hadn't determined the reason why. I found this website of links to have the most comprehensive list to help to figure out what might be going on: Coral Diseases and Parasites

One last link, older article, but found it also useful, "Old Tank Syndrome", does it really exist?: Feature Article: Old Tank Syndrome - Advanced Aquarist | Aquarist Magazine and Blog

Good Luck
If it is happening randomly, especially one or two a month and attacking colonies that were initially fine... then it is definitely an evil acro-crab. This little bugger was the cause of months of pain... I found him accidentally during the tank-tear down. They do not host in the colony, rather in the rock near the colony and emerge to slowly nibble away at the base until RTN takes over and kill the colony.


Old tank syndrome is phosphate saturation, or simply the end-stage of eutrophication in our tanks. It is cause by folks thinking that deep sand, algae-refugiums, and critters will do the export for them... and instead it is holding on to phosphate until saturated and then the system reaches a nasty end.
 

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Aquatic Philosopher
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Based on this I clearly have coral crabs that should be ok. The polyps look fine other than the bleaching of the tissue... I don't see any RTN or STN. Any recommendations on what I should do to try to reverse this bleaching, or just sit back and let nature take its course? I have a ruby crab that I have seen often toward the top of my tank but I have never seen him picking at any corals.
A ruby crab could be the cause. Mithrix crabs are know to eat SPS. I had a emerald that would go after some of mine before I got him out.
 

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Discussion Starter · #11 ·
I was also thinking.... I superglued this piece onto the rock but the glue didnt take so well. The piece is standing upright supported by the glue around it but it wiggles a little if touched. Maybe current in the tank is rocking it a little causing some friction that is irritating it at the base..... Perhaps I will remove it from the base rock and lay it down to heal... What do you think?
 

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Discussion Starter · #12 ·
LFS guy also said possibly the ruby crab. I will try to catch mine with a bottle trap this weekend. Do you think it could be from not enough light? I have mine up high under 10 T5 tubes.... The bulbs are 3 months old.
 

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Aquatic Philosopher
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Not lack of light... lack of light will cause the polyp density to decrease and for the tissue to loose color... and then recess. The image is of a very distinct patch of all tissue missing with healthy, dense polyps nearby. That is definitely predation
 

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Discussion Starter · #14 ·
The tissue is all there and the polyps are extended still.... Its just bleached in those spots. Thanks again for the help. Good to know. I will remove the ruby crab and put him in my sump as I am guessing it is the suspect. The acro crabs that i have are living in the corals and are the acceptable kind. Thanks again!
 
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