pockets anaerobic gas are no myth....unfortunately

[gregga]

Hey all......
Just wanna post this so maybe no one else will make the same mistake I did. I keep 12 tanks and about 200 fish and have been in the hobby about 8 years.
Anyway, I have a 20G high which about 6 months ago I placed under a 55G on a wrought iron stand. I was using the tank to growout 20 Labidiochromis Mbamba fry. But because of the height of the 20 there wasnt ideal access into the tank. Add that to the fact that placing the tank so low to the ground made gravity less than helpful trying to siphon and do water changes. This is the only one of my tanks that I sometimes need to resort to using a bucket. I normally will clean the gravel/sand in my tanks when I do water changes, however this substrate had become pretty packed down (apparently trapping the gas). Well, last week I moved the tank to a pedestal in the corner of my fish room & did a water change. After only about 10 seconds I saw some large bubbles coming out of the substrate. No more than 30 seconds after that every fish in the tank was dead. 6 months wasted. I'd consider myself an experienced hobbyist who rarely loses fish. I'm sure most of us have heard of anaerobic bacteria. Well, I can vouch for the fact it is real....So if I can help someone else not make the same mistake.........
The good news is that Mbamba female is holding again......

[Bristlenose Chuck]

That really sucks. I'm sorry, and I hope things work out better for your fry this time.

[ChEeRs_BiG_EaRs]

man, im so so so sorry eh. i would hate that. espicially the fact that they were fry that u had bred :(.
hey, can u please go into more detail on what this gas is, cos im quite intrigued cos i think one of my lfs has it :S
cheers

[Matak]

Am I right to assume that that couldn't happen in a moderately planted tank?

[RTR]

Anaerobic pockets can and do happen in a moderately or heavily planted tank.

It is not the H2S in the pocket that gets you, it is the disturbance that releases it into the water column.

[ChEeRs_BiG_EaRs]

so how does it get there in the first place?

[OrionGirl]

It's the natural result of bacteria breaking down nitrates. These bacteria only thrive in low oxygen areas, such as deep substrate that isn't disturbed regularly. Plants help, since their roots wiggle through the substrate, but not enough to prevent pockets. Shallow substrate, UGF, or regular cleaning in the entire substrate, especially under rock/wood will prevent it.

Of course, it isn't bad that it happens, it's just bad when the pockets are distrubed.

[TomFromStLouis]

Is this gas the reason occasional big bubbles come up from my gravel? If the bacteria in the gravel produce this stuff, I guess it is good to see the occasional gravel burp. Another good reason to have slightly larger than fine sand substrate I guess. Thanks for the cautionary tale.

RTR, you say the gs is H2S? In english that is sulfuric acid?? And what did you mean by "It is not the H2S in the pocket that gets you, it is the disturbance that releases it into the water column." ?

What exactly is it that killed the fish?

[OrionGirl]

Left undistrubed, additional bacteria will break down the by-products into harmless components. This is the normal process in many lake and pond beds. When it's disturbed, instead of being harmlessly contained in the substrate, it gets spread all over the tank and in the water 'at-large', so to speak.

[gregga]

RTR and Onion Girl have it right..........

Hopefully this post will help others.........thanks for all the replies....

Gregg

[wetmanNY]

Tom, the gas is hydrogen sulfide. OrionGirl, what they are metabolizing is not nitrogen in any form but sulfate to sulfide. They only do it when nitrate is exhausted. Other bacteria in the same community are making a living oxydizing sulfide back to sulfate. All happening quite deep, and in a sediment that remains undisturbed, like gregga's.

"Burps" from the gravel, if it's deep and also organically enriched, could also be methane, which isn't very soluble. But isn't the likeliest "burp" gas just carbon dioxide? Or would CO2 always remain in solution?

If gregga's fish died of H2S poisoning, the unmistakable, gag-making odor would have filled the room. Hydrogen sulfide is not merely skanky-smelling. It's as bad as shaking ammonia with bleach. Other nasty sulfurous smells, like onions gone rotten, are thiols a.k.a. mercaptans.

What about the alternative possibility? That normal processes of bioacidification depleted the carbonate buffer and pH had dropped; harmless NH4 had built up, since nitrifiers go dormant at pH in the low sixes; then when most of the water was removed in order to shift this 20-gal. tank and was replaced with fresh, the buffering was instantly renewed, NH4 converted to NH3, and the fish were overcome with ammonia poisoning. What is sometimes called "Old Tank Syndrome."

[OrionGirl]

Thank you , wetman--mental notes corrected!

[TomFromStLouis]

The authoritive tone and use of words I don't understand definitely makes me think you are right:) .

Could NH4 really be converted into NH3 so quickly that the entire tank-o-fishies die off in 30 seconds? If the conversion is a chemical one (not needing bacteria), then I can see it and do not doubt you have explained the disaster.

[OrionGirl]

You'll want confirmation, but NH4 is ammonium, while NH3 is ammonia. The additional hydrogen atom in NH4 prevents it from bonding with fish gills, which is why products such as amquel can be used to detox chlorine--it pulls the chlorine apart, which results in ammonia, and then adds a hydrogen atom to the ammonia. Bacteria can (I think) use either form, but only ammonia is toxic to fish.

Did I get that right? :)

[Matak]

The authoritive tone and use of words I don't understand definitely makes me think you are right .
All in favour say aye. *AYE!* The ayes have it. Wetman is correct. :D

[wetmanNY]

...but I don't want to be the Mayor of Baghdad...

.

.

but, yes, it is a chemical reaction, and it happens practically instantaneously, as the carbonates meet the NH4.

[RTR]

May I nay?

The nitrate->nitrite reducers, and the nitrite->ammonia reducers, plus the ammonia-N2 reducers are anaerobic, that is the they operate in conditions of very low oxygen tension but not absloutely oxygen-free. The sulfate->sulfide group are absolutely anoxic, not just anaerobic - these are two different culture conditions.

The two commonest gases released from substrates are CO2 (so that part is potentially correct) and N2. I don't know which is really more frequent. Methane and H2S (which is, as wetman NY stated, hydrogen sulfide) require more extreme conditions and are most often in tanks oxidized before they escape the substrate unless disturbed.

I also strongly qustion the likelihood or frequency of ammonium to ammonia change sufficient to kill fish. unless there is already significant ammonia reading in the tank, and you take the pH from below 6 to >10, it just isn't that big an issue. I would hope nobody here would do as much a log change in pH, much less four logs. No fish would survive that anyway. even the poorest of the hobby literature suggests no more than 0.2 pH change at once. The ammonium to ammonia shift from that would be undetectable.

[gregga]

ummmmmm.........sorry I started this........:rolleyes:
For what it is worth, the substrate in question was crushed coral.

On a happier note, the Mbamba female released about 15-16 fry tonight.. You're all aunts and uncles...........


Gregg

[125gJoe]

http://gordon.sourcecod.com/images/flagicons/american_flag.gif
Lots of good info here, but what's the best way to keep the "build-up" from happening? Would using something like an ice pick to disrupt the gravel deeply on some kind of a schedule prevent it??
Using large gravel for substrate is not an option for me...

[Matak]

Originally posted by gregga
ummmmmm.........sorry I started this........:rolleyes:
For what it is worth, the substrate in question was crushed coral.

On a happier note, the Mbamba female released about 15-16 fry tonight.. You're all aunts and uncles...........


Gregg
Don't be sorry. This is the type of challenge many of us enjoy digging into, whether it is determining what the problem truly is or just trying to keep up as we learn.

I agree with Joe. There is something for us all to benefit from here if we can prevent it from happening in our own tanks. I am somewhat concerned for my own tank because my planted substrate is a home recipe. What can we do to prevent a "build-up" of this nature from occuring?

[gregga]

The best thing you can do is stir up the substrate whenever you do water changes. This will keep the substrate from getting too compact........IMO....


BTW, Matak..I was just kidding......:D

[canucks]

I'd like to find out how to prevent this as well, if it's possible...
Isn't it kind of a no-no to stir up the gravel? I thought that it would end up suffocating the beneficial bacteria colony by burrying them. I would lean more towards the idea of gently dragging an ice-pick (or chopstick) through it. How deep is "deep substrate"? 3"- 5"?

[TomFromStLouis]

Isn't this fun? Two knowedgable folks politely trying to show us what actually happened. And a ringside seat too! OK, Wetman, you go into this corner here. No, the other one. That's it. You have explained a plausible chemical reaction but not defended RTR's statement that the gas was probably CO2 or N2, not the gas you need for your explanation.

RTR, please take the other corner over there. Good. You have rebutted Wetman admirably but not offered an explanation of what actually killed the fish.

Gentlefolk, go at it.:)

[wetmanNY]

Plus, I get to cut n' paste relevant paragraphs from www.skepticalaquarist.com and you'all (especially RTR) get to pull them to shreds. Then I sneak back to my cubbyhole and revise...

Thus:

"As pH drops, more and more ammonia is ionized to non-toxic ammonium. Here's a useful rule-of-thumb for the ammonia/ammonium ratio: for every one unit decrease in the pH measurement there's about a ten-fold decrease in the percentage of toxic ammonia. At pH 7.0 ammonia is about 0.33% of TAN, at pH 6.0 toxic ammonia represents only 0.03% of the total. The temperature comes into play also: at higher temperatures, more of the TAN is toxic ammonia. At 82oF there's almost twice as much non-ionized ammonia as there is at 68o, if the pH remains the same. There's a good presentation of these processes in a fact sheet posted by the University of Florida's Soil and Water Services Dept. at http://edis.ifas.ufl.edu/FA031. Their Table 1 shows the relationships of non-ionized ammonia (NH3) to pH and temperature. With the table you can calculate the fraction of toxic un-ionized ammonia represented by your ammonia test's TAN at your pH and temperature levels."

I've been going on the basis of this table. (follow that hyperlink).

RTR's right about the way bacteria with different metabolic requirements tend to stratify themselves in an undisturbed sediment. It's a question of opposed gradients, with, for examples, diminishing supplies of oxygen and nitrogen diffusing down that interface with diminishing supplies of oxidizable sulfide diffusing upwards. Each kind of bacteria find an ideal niche, stabilized by the metabolic requirements of their neighbors in the strata just above and just below.

One way to avoid troubles is to have a substrate that's no deeper than plant roots require (and aquatic plant roots tend to grow sideways into a mat called the "rhizozone"), and that's not enriched with sulfur-laden biodegradable organic matter (like fishfood stirred down there at the last gravel vacuuming).

The question in retrospect is, would gregga's fish have survived if the water had been drawn down, but the substrate remained undisturbed? I think they would have been done in by the ammonium/ammonia conversion anyway. RTR doesn't think so.

[beviking]

Wait a minute! Cut and pasting from your own site?! THAT doesn't sound too sound. Could've made it all up!;) j/k (Raises poster that says "skepticalaquarist.com #1")
Getting back to RTR's statement, unless there was a ph swing (which most likely wouldn't have been since gregga is an experienced hobbyist), the ammonium to ammonia swing doesn't seem likely. If, however, it had been a while since water changes then maybe...

How about it gregga?? Any rotten egg smell before your loss? Which, by the way, I'm sorry to hear!

I didn't check out the ammonia ionization chart from the site, but if my "Fish Hatchery Management" book has it, I'm sure it's everywhere.

[wetmanNY]

RTR hasn't posted a link to his good article on "Old Tank Syndrome": http://www.tomgriffin.com/aquasource/oldtanksyndrome.shtml

(btw, the Skeptical Aquarist site got started as a way to keep from re-posting the same material over and over... )

[ChilDawg]

For the sake of the Glossary, what is "TAN"? The link isn't working any more.

[RTR]

Love these acronyms - TAN = Total Ammoniacal Nitrogen (i.e., the total nitrogen from both ammonia and ammonium).

My argument is just that anyone who fiddles with the tank other than straight water changes with any positive, hobby-kit detectable ammonia reading is a fool. Ditto anyone who would do a log pH change is equally a fool. That is a ten-fold change - and while I generally agree w/wetmanNY that most "pH shock" jest ain't so, 10x change is beyond the Pale.

I get substrate bubbles, but I do plenums and I bet on N2 (no odor). I do have denitrification going on actively in those tanks.

My techniques for avoiding anoxic pockets:

In planted tanks use any depth of substrate desired, but plant heavily and renew the substrate every 1-3 years by cleaning out the old organics (largely dead root mass - swordplants, dense crypt stands, and Val stands are all offenders here).

In unplanted tanks have no more than 1" of substrate unless it is RFUG and full-depth vacuum with every partial - if you cannot cover the entire area each partial, mark with a rock/pebble and start there next week. Don't use sand. I know it is popular now, but I have had problems in the past and have long ago given it up. My techniques, not yours, my choice.

BTW, I disagree with the concept of a rhizozome applied to fish tanks. IME, the roots go down to the bottom of the tank, period, even with >6" of substrate or with plenums. They will generally occupy the full depth, only certain plants root as much laterally as vertically (Crinums are notorious). Crypts and Val send out prominent runners with development of daughter plants (vegetative propagation), but each plantlet roots vertically - check where the plants hit the glass and run along it.

BTW, The Skeptical Aquarist is one of the safest sites to cut and paste from - even if I don't 100% agree with all of it. I don't even 100% agree with stuff I wrote a few years ago.

[Kirin Fang]

Wow, a 30 second killer? That's some crazy stuff...

That's sucks....Sorry about your loss...

I guess I don't have to worry about that too much because I vacuum my gravel when I do water changes.

[gregga]

Hey Beviking........

There was no noticeable "rotten egg" smell while moving the tank. For what it's worth I tested the water about 1 week before the "accident" and less than 2 hours afterward. There was only a .2 change (8.0 to 7.8).......................Gregg

[TomFromStLouis]

I am learning a lot here but I still am not sure what killed the fish.


Oh well, if I follow RTR's advice I guess I need not worry about it.

[carpguy]

Well that leaves us in a pickle. No sulfurous egg odor and no large scale pH swing. Any other ideas?

I've been poking my nose in and out of Diane Walstad's book for its section on exactly this stuff. I'm more confused then ever :confused: :eek: . I think I really need to sit down with a chemistry book at some point. :rolleyes:

Gregga, sorry about your fish :(

[ewok]

Originally posted by gregga

For what it is worth, the substrate in question was crushed coral.


HUGE arguement against any ph swings but down, unless your water change was with liquid rock. the substrate in question kills the "old tank syndrome" theory also, the natural buffering capacity of the crushed coral substrate would prevent the formation of NH4 (ammonium), or at least keeping it from being concentrated. at the ph the crushed coral would create it should all be NH3 (ammonia)... it sort of rules out the massive release of ammonia theory. with the substrate in question, you should have a fairly stable but high ph.

a "normal" sand or gravel substrate might lend credence to the theory, but not crushed coral. the same principles just don't apply.

sorry for ressurecting this, but i followed it from another thread.

edit: i tend to lean towards rtr's theory, or maybe something like an overwhelming release of bacteria.......

[TomFromStLouis]

Please do not apologize for resurrecting one of the more interesting threads this forum has seen. I for one am glad to see it again because I never came to a conclusion as to why the fish died.

RTR rebuffed Wetman's chemical reaction explanation but never to my simple brain explained the cause of death. Maybe it was lost in the chemistry - I am not sure.

Either way, can someone, anyone, tell me in plain terms why the fish died so rapidly?

Then, also in plain terms, tell us what precautions those of us with fully planted tanks should take? RTR's Old Tank Syndrome article mentions removing all but Crinum roots and replanting from time to time to get old dead root structures out of the tank. Is that it?


I apologize for harping on this whole thing but this kind of full tank disaster is what keeps me awake at nights. If an aquarist of Gregga's experience level can lose it all in 30 seconds, I want to understand why and how to prevent it from happening to me. Thanks to all who contribute.

[RTR]

Tom?StL - there is a newer thread on DSB in Freshwater that picked up and ref'd this thread repeatedly. I don't have the URL, I believe scott started the thread.

And I don't know what killed the fish. But I do know why it happened - an untended heavily organic substrate (and very likely anoxic) was disturbed suddenly and massively. That is an absolute no-no. If such a situation comes about, remove all the livestock before disturbing, repalace all the water afterward, and run carbon a few days before introducing test fish.

[Tiger15]

Here is an experiment you can find out the content of the gas. Invert a clean transparent plastic cup over the substrate and disturb it until enough gas is collected at the top. Get a syringe and punch the plastic to collect the gas. Prepare a test tube with distilled water and bubble the collected gas through the test tube water. Use your nose to smell anything unusual while you are bubbling the gas such as rotten egg or ammonia smell. Check the test tube water later for ammonia and pH. I don't know of any sulfide test kit readily available but your nose may be the best tester.

I don't keep plants and all my tank substrates are kept to less than 1/2 inch. When I do water change, I vacuum the substrate wall to wall and also disturb it to disperse the dust. Despite regular cleaning and thin layer, I still observe bubbles from underneath rock and where the fish piled up the thickness. I suspect that the gas is mosly nitrogen and methane as the two are insoluble. The toxic gas like H2S and ammonia are highly soluble and I don't suspect they can be present in my substrate with the way I managed them.

[wetmanNY]

Tiger, my amateurish reading tells me that you're right about methane not being readily soluble, but that you're not right about nitrogen.
At a University of Idaho website I googled-- www.chem.uidaho.edu/~honors/airsol.html -- I read: "oxygen is almost twice as soluble as nitrogen, but since there is four times as much nitrogen in the air as there is oxygen, we'd expect to see twice the molarity of nitrogen in water as there is oxygen."

[Aderynglas]

Well reading this thread has got the synapses afiring and the brain cells aworking and from the depths of my memory came an idea about toxic lakes in Scandinavia (funny how fishkeeping makes the most obscure things highly interesting)

I can't help thinking that the main thing that would kill all the fish in the tank so quickly is co2 sooooo.....

I did a search on google and guess what??? There's information which I think will shed light on the matter, even involving the coarse coral gravel substrate - in fact I think its crucial to the info on this site.

Here goes for trying a link

toxic lakes (www.ace.mmu.ac.uk/Resources/Fact_Sheets/Key_Stage4/Air_Pollution/13.html.)

By the way, is it possible that the pH test wasn't working properly and gave a false recording of pH ???

[Aderynglas]

AAAARGHHHHHHHHH *&^^$£!"$%%^& links

try this

www.ace.mmu.ac.uk/Resources/Fact_Sheets/Key_Stage4/Air_Pollution/13.html

[Aderynglas]

GRRRRR



http://www.ace.mmu.ac.uk/Resources/Fact_Sheets/Key_Stage_4/Air_Pollution/13.html

[RTR]

I did not test the links, but if that is the coverage of the African toxic lakes which suddenly boil and wipe out villages, that is fascinating stuff. The attempts at abatement are intresting also - but I wonder about them long-term - a bit tech-heavy and costly for the third world.

[wetmanNY]

That "killer gas" that burped out of a West African lake twenty years ago was CO2: http://cooltech.iafrica.com/science/211366.htm

Aderynglas' link refers to acidification of European lakes, where aluminum becomes soluble and toxic as pH drops below 5.0.. In the aquarium copper from an old round of medication can become soluble again as pH drops, and poison fish.

But gregga reports that there was no pH drop.

[Matak]

.

[RTR]

BTW, the use of crushed coral does not preclude the presence of ammonia and ammonium in the deep substrate. Why do you think DSBs and plenums lose mass over time? The deeps are acidic and mobilizing calcium and carbonates, and the buffer provided in the water column only promises that dangerous titers will be somewhat more dangerous due to the higher pH. But it takes a lot for ammonia to be rapidly fatal - a lot.

I have no clue as to how much NH3/NH4+ could be in a deep and toxic substrate - I don't want to find out the hard way either.

[DaveinSF]

Excellent post, wetman. Based on our experiences with my girlfriend's tank, I think that a culprit of H2s buildup and poisoning is the decay of plant roots and plant matter under the surface of the substrate (which in our case was fine aquarium sand).

In our case, she had a lightly stocked, planted tank, but with a tendency for the ammonia readings to start climbing after only a couple of days after water changes. We thought this very puzzling as the tank was already mature and cycled and there was no discernible source of such high ammonia levels. One day she came home to find that all of her fish were suddenly dead. So we emptied the tank and prepared to take out the fine sand when after a little digging-- lo and behold! An INCREDIBLY foul smell like raw sewage came forth. The source was apparently a mass of decayed plant roots that had been buried under the surface.

Up to that point, if a plant died, she would take it out, but not get all of the roots, which were then left to rot under the substrate. I think it's important to make sure to get the entire root system when pulling a dead plant out of a live aquarium.





Tom, the gas is hydrogen sulfide. OrionGirl, what they are metabolizing is not nitrogen in any form but sulfate to sulfide. They only do it when nitrate is exhausted. Other bacteria in the same community are making a living oxydizing sulfide back to sulfate. All happening quite deep, and in a sediment that remains undisturbed, like gregga's.

"Burps" from the gravel, if it's deep and also organically enriched, could also be methane, which isn't very soluble. But isn't the likeliest "burp" gas just carbon dioxide? Or would CO2 always remain in solution?

If gregga's fish died of H2S poisoning, the unmistakable, gag-making odor would have filled the room. Hydrogen sulfide is not merely skanky-smelling. It's as bad as shaking ammonia with bleach. Other nasty sulfurous smells, like onions gone rotten, are thiols a.k.a. mercaptans.

What about the alternative possibility? That normal processes of bioacidification depleted the carbonate buffer and pH had dropped; harmless NH4 had built up, since nitrifiers go dormant at pH in the low sixes; then when most of the water was removed in order to shift this 20-gal. tank and was replaced with fresh, the buffering was instantly renewed, NH4 converted to NH3, and the fish were overcome with ammonia poisoning. What is sometimes called "Old Tank Syndrome."

[jpappy789]

This post is four years old...

[wataugachicken]

still very interesting though. . . much better than pulling up classified ads for one fish from 2002.

[IceH2O]

:iagree:

Its post like these that offer a lot of info that need to be resurrected.

I know to drag a chopstick through my sand substrate and I do rearrange my plants pretty often. I see bubbles sometimes but real small. I also have a long wide straw I stick into the sand, that way if any gas is going to be emmited its going out the straw and into the air, not the tank.

This should actually be a sub sticky IMO.

[Blueiz]

This is a very informative thread. The information provided in it can not be "started new".



still very interesting though. . . much better than pulling up classified ads for one fish from 2002.


Very well said..

Lets please not take this thread off topic.

Thanks,
Blue