RTN in stable tank- flow issue?

[thebookshark]

Howdy folks,

I had one of my smooth-skinned acros (I think it was a ‘Red Ferrari’ frag) up and RTN on me this week after growing well for 3 months. I tried fragging off the remaining healthy-looking piece but no dice- gone the next morning. All other corals and inverts, including a small (1.6”) crocea clam, healthy and growing. The acro that RTN’d was in a sort of nook in the rock work on the far side of the tank which is a pretty low-flow area. I also had my return pump lose power on me about a month ago so I’m using a less powerful backup until the replacement comes from the manufacturer. So I suspect it was a flow issue? Especially given the location of the frag that died. I don’t have a wavemaker/secondary powerhead in this tank for aesthetic reasons- it’s a peninsula on the raised bar area of my kitchen/living room and I don’t like wires running everywhere. But obviously wires look better than a tank of dead coral so I can add one if that’s what’s going on.

I know RTN has myriad causes and it can be very difficult to pinpoint, but in a tank with very low nutrients and stable parameters this is all I can think of. It does not appear to have spread (as of yet) to any other corals and I feel like if it was microbial in origin (vibrio etc) I would’ve seen others affected by now. Photo shows the acro that melted so you can see location in the tank.

In case anyone needs the following info, here you go:

21G UNS AIO peninsula tank
Kessil AP9X
RO/DI water, AquaVitro Salinity 1.025
Temp stable at 80 (though I did dial it down a degree today in case temp was a potential factor?)
pH 8-8.2 across the day
KH 8
NO3: 0.2
Phos: 0.06
Ca: 420
Mg: 1350

 

[jd22]

did you recently change or add any GFO or carbon?

I had some acros RTN after changing out some media

 

[thebookshark]

Nope. The only change was that I switched my KH dosing from a supplement with Ca & Mg to plain baking soda for a bit because my Ca and Mg were high (Ca 500+ and Mg 1500). But I tested before and after dosing and there were no big KH or pH swings. I e since switched back in case this was the culprit but if that was the case I imagine other coral and/or sensitive inverts would’ve shown at least some signs of stress?

 

[siege]

Common causes of RTN appear to be fast changes in alk, salinity, temp, lighting, and bacterial infections.

Unquestionably though, changes in flow will affect some corals, too. I don't know that was your problem for sure, but I wouldn't entirely discount it.

Big thing, tho, when was the last time you had an ICP-OES done? If never... do one ASAP, before adding any new corals. You may well be critically deficient in something we don't even have good hobbyist tests for (like fluorine, in my case), or overly high on something else (again, in my case, it was bromine, aluminum and silica).

Definitely worth doing to be sure, before you spend as much or more on a new coral as the test itself costs (~$50).

 

[thebookshark]

Common causes of RTN appear to be fast changes in alk, salinity, temp, lighting, and bacterial infections.

Unquestionably though, changes in flow will affect some corals, too. I don't know that was your problem for sure, but I wouldn't entirely discount it.

Big thing, tho, when was the last time you had an ICP-OES done? If never... do one ASAP, before adding any new corals. You may well be critically deficient in something we don't even have good hobbyist tests for (like fluorine, in my case), or overly high on something else (again, in my case, it was bromine, aluminum and silica).

Definitely worth doing to be sure, before you spend as much or more on a new coral as the test itself costs (~$50).

Where does one get this done? I’m certainly open to it.

 

[siege]

Where does one get this done? I’m certainly open to it.

They're kits you can order online. Various places to get them, I went with Amazon for convenience's sake:

This is the one I did from ATI for $50.

Here is one from Triton Labs, also $50.

Here's another from Reef*Labs for $45.

Personally, I liked the ATI because it returns a good number of readings and ALSO includes a test for RO/DI water, not just salt, and it's going to be a little more generalized with its results and recommended corrective actions, where the Triton one is going to be focused on correction using the Triton method, which is a whole other can of worms. The Reef*Labs one looks okay, but it doesn't test RO/DI, and it was the RO/DI test that confirmed the silica in my tank was coming from the RO/DI filter, not another source.

 

[90gDreams]

They're kits you can order online. Various places to get them, I went with Amazon for convenience's sake:

This is the one I did from ATI for $50.

Here is one from Triton Labs, also $50.

Here's another from Reef*Labs for $45.

Personally, I liked the ATI because it returns a good number of readings and ALSO includes a test for RO/DI water, not just salt, and it's going to be a little more generalized with its results and recommended corrective actions, where the Triton one is going to be focused on correction using the Triton method, which is a whole other can of worms. The Reef*Labs one looks okay, but it doesn't test RO/DI, and it was the RO/DI test that confirmed the silica in my tank was coming from the RO/DI filter, not another source.

Fauna Marin also has one that includes the RODI test, just an FYI.

 

[thebookshark]

They're kits you can order online. Various places to get them, I went with Amazon for convenience's sake:

This is the one I did from ATI for $50.

Here is one from Triton Labs, also $50.

Here's another from Reef*Labs for $45.

Personally, I liked the ATI because it returns a good number of readings and ALSO includes a test for RO/DI water, not just salt, and it's going to be a little more generalized with its results and recommended corrective actions, where the Triton one is going to be focused on correction using the Triton method, which is a whole other can of worms. The Reef*Labs one looks okay, but it doesn't test RO/DI, and it was the RO/DI test that confirmed the silica in my tank was coming from the RO/DI filter, not another source.

Thank you! I’ll get one done. I also picked up a Nero 3 today and just installed it. Regardless of whether that caused the RTN, the tank as a whole will probably benefit from better flow. There were several dead zones collecting detritus and crud was always accumulating on my monti caps. Will hopefully cut down on my daily turkey-basting.