My Acros are browning, and I suspect hydrogen sulfide.

[serwobow]

Here is the long story - many of my acropora corals have been retracting their polyps and browning out over the last couple of months. I don't know why because they were doing pretty well for over a year, and I have made no substantial changes in my tank husbandry during that time. My montis, stylos, euphyllias, and everything else are still growing well and looking as good as ever, and so are some of the tougher acros, like a staghorn, a blue slimer, ORA frogskin and a couple others. So, this seems to be a problem just with some acros including (pink lemonade, garf bonsai, strawberrry shortcake, sunset millie, JF nightstalker, some no-names). I have also noticed an increase in cyano growth, and maybe that has something to do with the problem.

Since only about 1/2 the acros are affected, I do not think that this is due to a major chemical imbalance (though I reserve the right to be wrong). Salinity (1.0265), alkalinity (8.5), and Calcium, Magnesium, nitrate (5ppm), and phosphate (0.05ppm), have all been pretty stable for several months, with no major swings that I am aware of. Therefore, since I had no idea what the issue was, I did what most people do - I increased the frequency of my water change schedule. This, unfortunately hasn't helped the sensitive acros yet, and some seem to be STN'ing from their bases, making it less likely they will recover before I can fix this mysterious issue. Then, yesterday, I was doing a water change, and decided to suck some of the gunk out of my sump, and I got blasted with a hydrogen sulfide smell. I am now suspecting that some of this H2S is making its way to the main display and causing some stress in the more sensitive corals. Then I got to thinking that my sandbed is now 10 years old, and I am sure it is probably making H2S just like my sump.
So, now I want to get rid of my 3" sandbed, in addition to clearing out all the muck from my sump.

Anybody have a similar experience with hydrogen sulfide being produced in their tank?
Anybody have any suggestions for sucking the sand bed out?
Do I need to worry about my live rock breaking or cracking through the bottom of my tank, since right now it is all just sitting on the sand?

Tank specs:
10 year old 50g mixed reef, about 50 different corals, mix of SPS, LPS, and some softies.
rabbitfish, 2 pink skunk clowns, 6-line wrasse, pygmy angel, yellow-tail damsel
Reefbreeders LEDs plus lumen bar
Tunze 9004DC Skimmer

 

[Andy V]

I doubt that you will have issues with the live rock breaking the glass, assuming it is of a decent thickness.

As for hydrogen sulfide, I do have some bad experience with that, although not similar to yours. I went through a brief period of trying biopellets in a reactor. During a water change, I realized that I had shut off the valve to the reactor, and without thinking, just opened it. It had been closed for a few days at least. That released all of the built up gas right into the tank. I had a few fish die immediately. I cannot remember if I lost any corals (I don't think I did), but they were closed up for several days. I had mostly zoas and LPS at the time. The SPS I did have was easy stuff like green slimer.

 

[dz6t]

I guess you are experiencing the so called “old tank symptoms”, which largely related to old sand bed.
The bottom of sand bed creates an oxygen poor zone and hydrogen sulfide is one of the by products from bacteria converting nitrate to nitrogen gas. The oxygen source is sulfate, which is a big part of sea water, and it gets reduced to hydrogen sulfide, which is harmful to coral and fish.

Different coral has different tolerance.

 

[wish]

Have you dip any of your sps? Look at the base of your sps and see any eggs.

 

[scavdog]

I agree with @wish. Acro eating flatworms wreaked havok in my system.

 

[serwobow]

Have you dip any of your sps? Look at the base of your sps and see any eggs.

I will look closer. I haven't seen obvious bite marks, but maybe this is the cause.

 

[wish]

I would get some dip asap.

 

[frank180reef]

Re state ALK calcium and mag

What test kits

 

[serwobow]

Update on the browning. @dz6t was kind enough to inspect and dip a few of my browned out acros, and he found that they did not have any obvious pests. So that is good.
He also measured my phosphate, which was 0.03.
I got from him some acro power and reef roids, which I will start using in case the browning is a low nutrition issue.
And Dz6t also adopted my foxface, who had been chewing the tips on several acros - and probably contributing the problems. Thanks Dong!

Regarding other specific params like Ca and Mg, I need to re-check. I have done so many water changes recently (Instant Ocean), that I am pretty sure my parameters will match instant ocean.

Meanwhile, I have begun the process of sandbed removal. It is 10 years old, and has never been cleaned, so probably the corals will do better without it.

 

[serwobow]

On the plus side of being stuck at home, I managed to remove my sandbed 2 weeks ago. It took me about 4 hours to remove it all, partly because I kept all the pumps going the entire time, and kept adding new saltwater to replace lost volume, so as to minimize oxygen depletion or other poisoning. The sand was full of brownish muck, and I definitely smelled some hydrogen sulfide while removing it. Everything survived the process, and since then, several of my brown acros have improved their coloration. I have had some issues with GHA and dinos post-removal, but so far they are manageable . I think maybe my sandbed had become especially full of crud because my flow is not super high. I'ver always liked having a sandbed, but so far sand-free is working out fine.

 

[ECExotics]

I guess you are experiencing the so called “old tank symptoms”, which largely related to old sand bed.
The bottom of sand bed creates an oxygen poor zone and hydrogen sulfide is one of the by products from bacteria converting nitrate to nitrogen gas. The oxygen source is sulfate, which is a big part of sea water, and it gets reduced to hydrogen sulfide, which is harmful to coral and fish.

Different coral has different tolerance.

You are incredibly knowledgeable, I just learned something new too.

 

[Chris A.]

On the plus side of being stuck at home, I managed to remove my sandbed 2 weeks ago. It took me about 4 hours to remove it all, partly because I kept all the pumps going the entire time, and kept adding new saltwater to replace lost volume, so as to minimize oxygen depletion or other poisoning. The sand was full of brownish muck, and I definitely smelled some hydrogen sulfide while removing it. Everything survived the process, and since then, several of my brown acros have improved their coloration. I have had some issues with GHA and dinos post-removal, but so far they are manageable . I think maybe my sandbed had become especially full of crud because my flow is not super high. I'ver always liked having a sandbed, but so far sand-free is working out fine.

I had to change out the sand on my old bio cube and it was completely full of crap in 1 year. Can’t imagine how much gets built up over a few years. I love the look but won’t put up with having to remove sand again

 

[GobyWanKenobie]

I'm glad you solved your problem. I prefer sand, but I do know what you're referring to. With every water change, I vacuum/siphon a portion of the sand bed. It's amazing how brown the water is that goes up the tube. The smell is very distinctive. I have been told by at least one other reefer that this is not a good idea, but I think it helps to keep the sand bed fresh. Granted, there are portions of my tank I can't access, but I'm hoping that by cleaning 3/4 of the sand bed, I can avoid "old tank" syndrome. Happy reefing!

 

[frank180reef]

I dunno display sand bed is Very old

 

[GobyWanKenobie]

I dunno display sand bed is Very old

Other than your snails, does it ever get disturbed or stirred?

 

[frank180reef]

No

 

[serwobow]

The thing that was remarkable to me was that I have a mixed reef, and all of my non-acroporas were doing great (several montiporas, several euphyllias, softies, anacroporas, leptos, others). Even about 20% of my acros were doing well. Now, it looks like about 50% or more of my acros are starting to do well, though it is too early to be certain. It is commonly known that acros generally are more finicky in reef tanks, but the exact reason for their difficulty has never been found, as far as I know. Well, I think that something in my sandbed was causing the difficulty in my case.

 

[serwobow]

I think one possibility as to why acroporas are more difficult is that they are better at sensing and responding to bacteria and bacterial products in the reef tank. Benthic bacteria are different than planktonic bacteria, and the sandbed can certainly host more and different bacteria than the water column (especially anaerobic bacteria).

The paper below (and others like it) found that acroporas have lots more bacteria-sensing genes than other corals. This may give them enhanced ability to respond to bacterial products in general. Many of these receptors drive inflammatory responses. It is possible that these extra genes enable acroporas to be the first to respond negatively to high levels of potentially pathogenic bacteria in reef tank.

Voolstra, C., Li, Y., Liew, Y., Baumgarten, S., Zoccola, D., Flot, J., Tambutté, S., Allemand, D., Aranda, M. (2017). Comparative analysis of the genomes of Stylophora pistillata and Acropora digitifera provides evidence for extensive differences between species of corals Scientific Reports 7(1), 17583. https://dx.doi.org/10.1038/s41598-017-17484-x

“Hence, it will be interesting to see whether A. digitifera (and perhaps other Acropora species) represent indeed ‘extreme’ cases of expansion of innate immunity-related genes (even within corals) and whether this might even be a hallmark of coral species from the complex clade. With more coral genomes expected to becoming available soon, this will be a fascinating question to pursue. Complementary to this, expression-guided studies might help to further illuminate this point by provoking an immune response in a range of coral species and comparing overall expression patterns as well as identifying the genes and pathways that respond. This might also help to grasp why different coral species harbor such physiologically diverse tolerance levels to environmental stressors.”

 

[frank180reef]

No

Oddly I removed sand previously undisturbed for years no real smell

 

[serwobow]

Maybe your tank had more and better current than my tank. So much organics had settled in my sand that it seemed almost like mud in places. And it smelled like hydrogen sulfide (though not terrible). Also my sandbed was about 3 inches deep, so maybe that was an issue too.