Why the acro/birds nest tissue recession?

[scolley]

Why did my acro RTN? And why am I getting tissue recession in my birds nest?

I've got a small (29g) mixed reef. 1.5 yrs old. Have had some form of SPS in it from the start. A few weeks ago I noticed a fairly new acro was getting little to no polyp extension. Everything else was fine. A couple of weeks later, it RTN'ed in about 36 hours. One colored tip remains.

And a birds nest colony, previously growing like gang busters, is now showing tissue recession. Not from the bottom up, but in the branches. PE is still fine, even on those areas where the flesh is off the coral.

What gives?

My parameters:
pH: 8.3
Temp: 79.1
SG: 1.0265
KH: 7.85 dKH
Cal: 415 ppm
Mg: 1320 ppm
Po4: 0 ppm
NO3: 0.5 ppm
light: @400 par


Chilling and heating keeps temps level. Peristaltic pumps supplying 2-part keep KH from swinging. Small (2-3% system volume) daily automated water changes prevent any w/c based swings. I test the water each weekend - no drifts off of targets - except salinity, that I rarely check. The 1.0265 was too high, and has since slowly been brought down to 1.02525.

 

[scolley]

A bit if additional information may be appropriate. The tank has been stable, except as follows:

1. The acro itself is new - only 4 weeks in my tank.
2. I got an RBTA in the same time frame. No wandering. Nowhere near the SPS.
3. I got a 1.5" ornate, orange legged hermit crab just before I noticed the tissue recession. Is in sump now.
4. I started using "Night mode" on my Vortech just before the tissue recession, dropping circulation by 50% at night. Normally the MP10 runs full power in Reef Crest mode. Have reset back to 100% 24x7 now.
5. Curiously, I lost a small acan colony - on the sand, no where near the high up SPS - within 24 hrs of the RTN'ing of the Acro. It RTN'd too, from healthy to white skeleton in 36 hours. But it is in crowded conditions on the sand, and I assumed some other coral got to it over night. All my other acans (all corals actually) appear fine.

I can find no evidence of AEFW or any other critters on the corals.

Maybe my acro died a slow death from lack of light, and my birds next tissue recession is unrelated? Thoughts?

Thanks.

 

[smtank]

Do you have any leathers in the system?

Can you post a picture, a macro shot if possible.

What type of acropora is it?

Did you try different placement with regard to flow?

And specifically what brand and type of lighting?

TIA

 

[scolley]

Thanks TIA. I'll try to get a macro shot.

The acro was a Glowstick Acro from Unique Corals. Here's a link. But that picture does not do justice to the fantastic polyp extension I was getting after it was in my tank a few days.

I did not change the flow, precisely because I thought the great PE told me it was happy. And it remained that way a few weeks, and then no PE. A week or so later, RTN.

The lighting is 150w MH DE Radium 20K, bulb approximately 11" from the coral, with the corals under 4-6" of water. Not deep. It's in an 24" Orbit, with 2 supplimental PC actinic bulbs. Because the corals are so high up, I don't think they get much light from the Actinic. Under these conditions the birds nest has been flourishing until very recently. Rapid growth. Have had it 9 months to a year, but remained fairly dormant until I switched from RC salt to ESV six months ago, and growth took off like a rocket.

Upon checking... I see that the Radium bulb has been in for 14 months. Time to change the bulb, clearly. But bulb aging is slow, right? So any deleterious affects of an aging bulb should happen slowly. Not like this. Right?

I'll see if I can get that macro shot...

 

[smtank]

Oh that is a beauty, very nice.

The alk is on the low end.

Dosing anything? Saw the pump for buffering but anything else.

Yes I would not have changed a thing if the PE was good, so frustrating.

Lighting sounds good, besides the old bulb.

I looked for a shot of your tank to see if any corals might be having some affect. In smaller systems I have had problems keeping leathers and sps together because of the toxins of the leathers. Running quality carbon helped but I had to get rid of the leathers to really make a difference.

 

[scolley]

Oh that is a beauty, very nice.

Yeah. Thanks. It's my first "expensive" acro that I've tried. So this is kind of a bummer. It was gorgeous (if small) with the full PE.

The alk is on the low end.

If we can assume that I'm correct about levels being very stable (due to AC Jr controlled peristaltic 2 part dosing through out the day, check for tweak need every weekend), is that too low? It's the level things have been flourishing at previously.

Dosing anything? Saw the pump for buffering but anything else.

Dosing 2 part as described above. I DO dose Mg every weekend, so that DOES swing. Too lazy to hook that up the other peristaltic sitting in the closet. No other dosing. Just small daily w/c w/ESV salt and food, primarily Rod's.

You asked about leathers. Yes. One small one has been in the tank for about 4 months. Don't know what it is exactly. Approximately 1.5" across, not upstream of the SPS, and I keep 1 1/2 cup bags of carbon in the sump, swapping a bag out every two weeks. Here's a pic. Maybe someone will know what it is.




Here's the poor little Acro. Kinda sad now. Since one tip has hung in there, I've just left it alone... did not want to add insult to injury by snipping off a tiny tip without knowing what was wrong.

BTW, beside the bleached acro is another SPS I got at the same time. Darned if I can remember what it was! But it's PE is clearly very poor also. Though it never looked too great from the first day I got it, so I did not mention it... not wanting to confuse the issue.

And here's the Birds Nest. Unfortunately my macro shot is aweful. So you'll have to take my word for this... If you look dead center, you'll see an area where the picture appears over exposed, washing out detail. It is. But in that same are the green polyps are still extended, but the orange flesh on the bone is receding. White bone showing in places. This coral is about 4" away from the Acro.

Too much information, I'm sure. Sorry. But didn't want to hold back potentially useful information.

Thanks for the help!

 

[smtank]

All information regarding the system is very helpful. And thank you for providing it and the pictures.

I dose Parts A/B as well, and some mg with routine water changes. I keep the alk around 9-11 and found my sps really like that range but that could just be my tank, 28 gal nano.

Yes that leather is too small to cause any problems.

Sometimes RTN just sets in and finding the cause is near to impossible. But the fact that you are not seeing the same PE on the other sps as well leads me to believe that something is out of whack with the water chemistry.

Hopefully someone else will be able to see the forest through the trees.

Good luck and following.

 

[scolley]

I keep the alk around 9-11 and found my sps really like that range...

Yeah... I've always kept mine on the low side of standard practice. However, it's also apparently within the range of some quite successful SPS keepers. I've always assumed the high Alk targets (relative to NSW) were set for the same reason many people set low salinity targets (again, relative to NSW), because the risk of swinging into too little Alk is bad, just as is the risk of too much salinity. But no matter. It's easy enough to allow my alk to slowly creep up to 9+ over the next week or two, and stabilize it there.

But that can't be my problem, as it's ALWAYS been in this range. And the birds nest problem is new. So it's something else...

Good luck and following.

Thanks for the help!