Is this STN?

[Laith]

I've finally gotten my tank to the point where I wanted to try SPS again. I had tried twice in the past but the corals died after one or two weeks and I never really saw any PE on those corals.

So, better lighting (Orphek LEDs: PR-156W), better NO3 (50 down to 4), better PO4 (2 down to .09), RODI (0 TDS) led me to purchase an acropora on the 25th of March.

I started it on the bottom of the aquarium and gradually moved it up over 3 weeks. The coral looks great, growing quite fast with new polyps on the tips, great PE...

and then I've noticed that the base is white with no polyps (see attached pic).

Is this STN?

If so, what can I do to stop it/save the coral?

Tank has lots of flow (250l tank, 30 liter sump) with 2x Tunze 6055 with a controller (on surge mode). 20l water change every week (Instant Ocean Reef Crystals). Tunze skimmer. Tunze ATO with kalk. Currently dosing 50ml of vinegar a day to try to bring down the NO3 more. Running RowaPhos and carbon (Rowa).

Other parameters:

Temp. 25.8C
Ca 530 (Red Sea kit)
Mg 1500 (Elos kit)
KH 8.4 (Hanna)
pH 8.1 (Elos)
NO3 4 (Red Sea)
PO4 0.09 (Hanna UL)

Thanks!

Laith

 

[mos90]

it looks like stn. that being said, your water parameters look good. po4 is a little high but shouldnt cause an issue.

normally i found three major things that cause stn.

1-lack of light or drastic change in lighting.
2-alk swings
3-adding large quantities of gfo at once.

 

[Laith]

Forgot!

Water is at 1.026 (calibrated refractometer)

 

[mos90]

ive never dosed vinegar so im not sure if that can cause problems.

 

[Laith]

Thanks for the input...

- I'm pretty sure the Orphek unit puts out enough light and I did take care in slowly moving the coral up.
- Alk is always between 8 and 8.5
- I've been using the same quantity of RowaPhos for awhile: 6 tsps, changed every week.

Would it be normal that an acro with STN would continue to grow well, with new polyps appearing on the new growth and great PE and color? I would think that if it was stressed/ill it wouldn't exhibit healthy behaviour like that...

 

[mos90]

redbugs or flatworms are also possible.

i have had an anemone sting 1 of my sps's. the tissue began to recede in that area but the rest of coral showed no signs of stress. i ended up fragging and it has since recovered.

 

[Laith]

Don't have an anemone...

And I don't see any bugs or flatworms.

So if it STN, what do I do? Can a coral recover by itself from that?

And if it isn't STN, what could it be?

Anybody else see anything like this?

I guess it is possible that it's growing well while a problem is occuring elsewhere on it: each polyp is a seperate animal no?

Any further inputs would be helpful!

Laith

 

[mos90]

the anemone scenario was an example.

a coral can recover IF you can figure out the problem.

it is some version of tissue necrosis.

the problem is that so many things can cause stn it can be very difficult to pinpoint.

example is i was dosing redsea nopox a while back on my 125. i decided i was not happy with the results i was getting so i discontinued its use. for some unknown reason within a week most of my sps's had stn or rtn. i had to remove all corals and save what i could.

 

[Laith]

Ok, thanks for your input!

Tomorrow I'm going to frag the coral and see how that goes.