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

 

[exnisstech]

Sometimes it just happens with acros and we never know the actual cause. Healthy one day dead over night. I run very similar parameters and lost a 3 yo colony a couple of weeks ago over night. Its the bane of keeping sticks. Most of what I've read lead towards a bacterial issue but I haven't read of any 100 % proof that's the cause and I don't know if anyone can predict it using test results. I just accept it and move on. Mine almost always seem to go bottom up. I managed to save a piece once that was top down RTN but I've not managed to save one starting at the base.

 

[Justfebreezeit]

That is definitely on the far side away from your only flow source so that could potentially be the issue.

I have the same tank with much more flow and also had a red Ferrari. The only coral this tank has killed so far actually lol. But I'm pretty sure mine was bottomed out p04 for to long.

Good luck.

 

[Ben's Pico Reefing]

I have found not all corals will be happy in the same tank. I had a healthy tank years ago and only 2 sps I could keep. Any other would due. I also had some that RTN and right when there was hardly any flesh left, it held and regrew.

If your other corals are happy, while there is always room to improve, some things aren't worth changing if everything seems happy and nothing out of the ordinary. With that said, lower flow area could have been a culprit. There is oxygen and other exchanges going on that corals especially so need the flow. But without a frag and someone looking under the microscope no truly way of knowing.