Acropora STN

[A_Lee]

I have an Acropora colony that is showing signs of STN from the base up. I have heard this is due primarily to either a lack of flow around the base, and/or lack of alkalinity. I am sure it is not my alkalinity, as everything else is doing awesome in my tank. I suppose it is probably a lack of water flow around the base, however I did have an Acropora piece there before, and it did pretty well until I got rid of it.
So, my question is ... if the tissue recession is due to a lack of flow, will the tissue recession continue up the colony until the entire colony is dead? Or will only the base lose tissue?

 

[tuberider]

IME light is usually the culprit, the upper branches shade the base of the coral and it doesn't get enough light to sustain the zoax. I have seen it in corals that don't get enough flow, but that is in extremely crowded conditions where you see it in more than one coral. Also, low alk can be a culprit, but I figure you've got that under control as you know what you're doing

 

[Ocean Treasures Aquarium]

I say a combi. of all 3. Usually its light for some of mine.

 

[Mr. Ugly]

I've seen that with high s.g. as well.

 

[A_Lee]

Thanks for the responses everyone! I appreciate the feedback

So, my alkalinity usually lingers around 10-12 degrees, which is high by some peoples standards, but it has never proved to be a problem for me. I dose two part solution every morning by hand.
With regards to the light, the base doesn't get a whole lot of light ... not to say it is in the dark either. I didn't know the lower regions not getting light would die though ... I thought maybe they would lose color, or not extend their polyps anymore causing the base area to look bare. In my case, I actually see skeleton.
In any case ... if it is flow, or light, will necrosis continue until the entire colony is dead, or only in the localized regions suffering from say, lack of light and/or flow?
The rest of the colony is absolutely bangin' though. When I first got it, it was brown. It now has purple tips, and neon green polyps! Reminiscent of a GARF Bonsai
The A. millepora, and A. tenius I have on either side (within 2-3") of this Acropora colony show no signs of tissue necrosis.
My specific gravity is at 1.025.

 

[tuberider]

I have a couple of colonies that appear to be part of the live rock due to STN, they are rather large (~1') and old though. One thing I have noticed is that with my larger tank the STN has stopped for one reason or another and the tissue at the bases of the colonies appears to be fat instead of thin.

 

[A_Lee]

Ah, so on some of your larger colonies, the base how no more tissue, and some algae growth makes the base of the cora look like a part of the rock huh? That sounds kind of neat
What does "fat" tissue look like? Because the base on my Acropora colony has NO tissue in some areas

 

[tuberider]

Ah, so on some of your larger colonies, the base how no more tissue, and some algae growth makes the base of the cora look like a part of the rock huh? That sounds kind of neat
What does "fat" tissue look like? Because the base on my Acropora colony has NO tissue in some areas

Actually I need to chop up one of the large colonies to make the aquascaping work, a big ORA Indo stag, the A. austera OTOH will remain because it looks soooo cool growing out of the rock like it is, I'll see what I can do about getting a pic.

AFA fat tissue, the area where the tissue meets the skeleton is raised because the coral is still calcifying, also the tissue is not thin, it is fleshy looking and slightly textured almost lumpy if you look real close.

 

[A_Lee]

I'll keep my fingers crossed on this colony, and hope the recession doesn't continue up the branches of the colony ... because like I said, everything else in the colony is doing fantastically with regards to coloration and growth!!

 

[tuberider]

How fast is the recession?

 

[DurTBear]

I would advise you to frag that Ant for back up. That was the first symptom of my tank troubles even though my parameters checked out. Before I knew it, the whole colony was gone along with other sps colonies in my tank.

 

[Mr. Ugly]

I dose two part solution every morning by hand.

[...]

My specific gravity is at 1.025.

S.G is measured with a refractometer calibrated with a reference standard and not RO/DI water?

It's easy for s.g. to creep up unnoticed when dosing 2-part.

 

[A_Lee]

@Tube -Not terribly fast at all ... I just noticed it about a week and half ago.
@Durt -I was thinking the same thing
@Mr.Ug - Yes, refractometer that is calibrated with BAR calibration fluid (35ppt).

 

[tuberider]

The STN I experienced in my old tank progressed over the course of many months, I'd be uncomfortable if you're seeing a noticeable difference over the course of a week.

 

[JAR]

Check for AEFW!
They are invisible unless you dip the coral and you can see them when they fall off. They might not fall off so blast them with a turkey baster too.