A possible explanation for STN events

hatfielj

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There are obviously many things that can causes stn/rtn, so this is possibly just one of them.
I am currently going through a slight stn event in my tank. Its not the first time but its the first in awhile and it's frustrating to say the least. My tank had been doing so well as of just 6-8 weeks ago so naturally I have been desperately trying to find a cause (I have no pests, my parameters are great, etc). I'll spare you the details but I think it was a combination of things causing too much stress on my corals even though they were very healthy.
One very important thing I noticed though was a major dinoflagellate bloom. I think this was precipitated by adding a bunch of new frag plugs as well as my skimmer not working for probably a week or more while I was on vacation.

My suspicion is that the dinoflagellates are actually a lot more harmful to the tank as a whole than I originally would have thought. My thought is that they destroy the tank's micro ecosystem. Meaning, I think they kill off good bacteria, phytoplankton, and the micro clean up crew (copepods, etc). We know they can kill crustaceans such as snails and crabs because we see it happen. So why wouldn't they also kill smaller organisms? Obviously if this happens a tank crash can ensue from the destroyed ecosystem. This is what I assumed was happening and today I looked up some info on copepod biology. It turns out that dinoflagellates are well known parasites of copepods! (I know, not very scientific, but hey I'm trying) https://en.m.wikipedia.org/wiki/Copepod
But if this occurs in our tanks, there is no way for them to recover their populations since its a closed system. Unless of course we replace them.

So, my solution at the moment (now that the dino's have mostly gone away) is to reintroduce copepods, phytoplankton, and beneficial bacteria to my tank in hopes that it will restore my previous ecosystem and hopefully allow my remaining acros to recover. I'll let you know how it goes! If this turns out to be helpful then in the future repopulating the tank with these beneficial organisms at the first signs of trouble may be a good idea.
 
following...
 
I'm dealing with stn right now my self. i have a very large piece of acro that just started losing some tissue. I'm going to cut that section off this morning and hope it stops. I also have noticed every maricultured sps i have every put in my tank had gotten stn. all other sps do just fine
 
STN is so frustrating. My tank has gone through bouts of it over the years and it's always hard to pinpoint the issue. I think it's typically due to some sort of irritant, in my case there is some red turf algae that is competing with my acropora. Dino's are probably doing the same thing in your reef.

I think establishing the proper bacteria can help overall, long with good husbandry, and like you're suggesting, to re-establish the eco-system. Keep us posted on the progress and I hope things turn around soon, keep that super-glue handy to stop STN!
 
I also have noticed every maricultured sps i have every put in my tank had gotten stn. all other sps do just fine
This is what is going on in my tank right now. I am getting the slowest STN I have ever seen, just millimeters a day to 2 different colonies both of which were maricultured pieces. I lost one maricultured piece 2 months ago to same super slow STN, then no die off until this past week. Again only to my maricultured pieces. I have 32 other Acros mostly frags and some colonies that were all from captive colonies that are doing awesome.
My parameters are perfect, ALK steady between 7.5 and 8.2. pH 8.0 night to 8.2 day. Dosing aminos. Feed every 3rd day. PO4 0.02. Nitrate undetectable.
Have fragged and saved frags from 3 of the pieces so far.
Really frustrating. And I mean the slowest STN ever. No pests, no bite marks, no red bugs.
 
Well, I've dosed some bacteria, added new clean up crew, and added a bunch of pods and cultured phytoplankton. Unfortunately nothing slowed this down. I basically had to frag all of my colonies off my rock work and the tank is now devoid of acros. My montis, acans, chalices, and zoas are pretty much untouched. So are my styloporas/pocilliporas. It sucks, but at this point I'm over it. I was able to re-aquascape the tank which was nice, so hopefully things will settle down and over the next few months I'll be able to start adding acros again.
I have all kinds of theories now. The only one that seems to make sense is that this was some sort of bacterial or viral infection. I think my corals got stressed out by lack of feeding, the dino bloom, and a couple of parameter swings and this left them susceptible to the infection. Nothing else seems to make sense. I had my water tested by triton and everything was good except my Iodine was too high (from dosing red sea part A). So now I wait and hope that this all goes away. It sure does suck to watch, but I guess that's life!
 
I have noticed that almost all of my maricultured pieces went south. when i noticed the STN, RTN i started fraging them. even some of the frags continued STN, RTN. I have read on a bunch of forums that it's tough to keep the maricultured pieces. all my acros that where pulled from the wild are doing fine so it has to be something with the way maricultured is cultured i guess
 
There's been no preference in my tank in terms of maricultured, aquacultured, or wild acros. All acropora/millipora had STN.
Another thought I had about these mysterious STN events that we all have is that perhaps its because we mix corals from all over the world? Meaning, we're introducing viruses/bacteria from say the Caribbean to corals that originate in the indo-pacific or other regions. Obviously those corals will have no active immunity to these new pathogens and if stressed (as happens in our tanks frequently), they could easily succumb to infection.
Just like humans have to build up our immune systems to various pathogens, corals probably have to do the same thing. Just a thought! I wish I could work in a marine biology lab and study corals! It would be exciting to try to figure these things out
 
How clean is your water. I often see tanks run with great parameters but their light to tank filth ratio is off haha
 
Ca around 450
Alk usually between 8-9, though it did fluctuate (dropped a little) before all this started
Mg has been 1200-1300
Nitrates barely detectable with salifert
Phosphate undetectable with salifert
I run a bag of activated carbon in the sump most of the time, nothing else.
 
Interesting theory.. Makes me think of other influences between organisms that could cause considerable imbalances yet nobody ever talks about them.
Though every time I hear about stn/rtn, most cases include this:
Nitrates barely detectable with salifert
Phosphate undetectable with salifert

But I've found not aiming for zero to be far more beneficial than not. Might not be the fix all as stn/rtn can be bacterial, viral, fungal, etc, etc, etc... It makes it really hard to solve some problems. But 9 out of 10 times, if I see rtn/stn, I just feed a heavy dose of nutricell every day, and then deal with the water afterwards. Otherwise lack of continuous food I think is a bigger problem than most realize.. Might be completely wrong but it seems to work for me each time. I even purposely buy corals that are in the 5$ bin at the LFS because he puts corals in there that have tissue loss. Then I get home with them and with the exception of a couple most come back. I do drip feed reef energy 24 hours a day, but the nutricell is a favorite and has a minimal impact on phosphates.

Hope things improve for you though! :(
 
So sorry to hear about your recent SPS bleaching issues. If I had to guess, I suspect you probably had a recent and sudden alk spike or alk drop that is causing the stn or rtn. Over time, those sensitive corals should stabilize since your parameters appear to be back to normal.
 
I have found that running carbon full time can cause issues. Also have you tested iodine?
 

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