What Might Cause Fatal Gas In Cory Stomach?

(just finished typing this out, sorry it's quite long)
On wed last week, I picked up 5 sterbaI cory from a local aquarist here in GTA. Four of the 5 died quickly on Friday afternoon evening.
The fish were bought direct from a wholesaler about 6 weeks prior, and kept in my friends tank since then. He originally bought 13, 8 died, the 5 are the survivors. The 5 were seemingly healthy for 3-4 weeks, ie all were eating, no deaths.
The tank (my tank) is a 40b, with blasting sand substrate. Lightly planted with low lighters. The tank is pseudo black water, with lots of driftwood, IAL, and even humic acid (small amounts). So the water is well stained with tannins, but remains somewhat hard. Working on it.
My parameters are all green. zero ammo and nitrites, nitrates low, pH around 7-7.5, tested via API master kit. Hardness is on the high side (180 GH and 80 KH, via dipstick).
I have had 6 pentazona barb in the tank, for the past 6 weeks, tank was newly set up prior to that, cycled with media from other tanks. The pentazonas remain healthy and vigorous despite the cory deaths.
What happened:
Friday afternoon, after work, I came home to 2 of the 5 sterbaI floating upside down. One was dead, the other not yet. When checked more closely in specimen container, the not-dead cory seemed to be swimming okay, but could not remain below surface without effort. I think it was exhausted from trying, and just floating to conserve energy. Both fish's bellies appeared swollen, but only from the bottom, ie not from the side. Within 2hrs, 2 more cories were floating, also upside down. So now I had 1 dead, 3 floating, and 1 okay.
All 4 survivors were removed to an Epsom salt bath in the specimen container for about 40 mins. During which time the 4th and final survivor also developed issues, lying on its side on bottom (but not floating).
All 4 survivors were then set up in a shallow hospital tank with tank water, heater and air only. I added Melafix.
3 of the 4 died before bedtime (ie within about 6-7hrs of my coming home and first seeing a problem). The sole survivor now appears okay, 3 days later. Skinny, but eating. Sadly, it's all alone in the hospital tank.
I autopsied the 3 evening deaths, and they had significant accumulations of gas in their stomachs/intestines. Not the swim bladder. I know it was the stomach/intestine because the gassy organ was long and tubular, and also had bits of food in various states of digestion. When I say gassy, their guts were like those long balloons clowns blow into shapes for kids.
So, what could have caused these symptoms? I know I won't get a specific diagnosis, because its so long after the fact, and I don't have cultures, preparations, etc. But what do all you helpful and lovely people think I should be considering, in terms of likelihoods, and precautions when getting more fish?
It can't (~is not likely to be) be systemic to the tank, because the pentazonas were and remain fine. It's got to be fast acting because they were okay for 2 days, then went belly up in a space of a few hours. I doubt it's food related, because the symptoms appeared almost 24hrs after last feeding.
My best thought/guess is an explosion of bad gut fauna (ie bacteria), but I'm lacking on a cause and mechanism.
Thank you all for your time and help!!

 

If you use sand as a substrate, I'm willing to be it was accumlated pockets of toxic gas that builds up from decaying matter in tanks with sand. You have to stir the sand, do it every time you change the water.

 

The gas in the stomachs was most likely a secondary symptom, or due to their bodies not working correctly anymore while they were so close to death. Unfortunately the fish sound like they may have been sick the entire time and it just took so long for them to finally succumb to whatever it was.

Yeeesh. A few weeks ago it was everything dying from old tank syndrome. This week its anaerobic bacteria creating epic gas bubbles in shallow sand substrates!

The cories wouldnt have ingested the bubbles that are extremely unlikely to have been in this tank anyway. They would have taken the hit to the gills and died nearly instantly from the poisoning.
Bottom line, don't be concerned with gas pockets in sand unless you can see them. If you see them forming under the substrate just poke them.

As to the deaths, its why I will never buy cories again. I had an impossible to cure disease that only affected my sterbais and eventually gave up and euthanized all but one. There seems to be such a problem with them these last couple of years.

What temperature were you keeping them at? They appreciate a higher temp than most other cories and I'm completely unfamiliar with pentazona barbs.

 

Thanks Whitewolf and Wraithen
Most of the tank only has 1-1.5" of sand, I'm intentionally keeping it shallow, and plants are either column feeders, or in the case of some crypts, they're in small dirted, cravel-capped bowls.
I'm interested in your cory thoughts wraithen, I've had very mixed results myself. This is my second time losing a batch of sterbai, the first was a completely different tank and situation over 6 months ago. Hmmm.
At the same time, I just bought 5 panda cories from a local big als for a tank I keep at my parents' place, and they seem to be doing happy and well. Grrr.
I'm thinking I'll get a few bronze cories, which are generally cheaper hereabouts, and do a trial run with them, sort of trouble shooting.
Tank is kept at 80F.

 

Thanks Whitewolf and Wraithen
Most of the tank only has 1-1.5" of sand, I'm intentionally keeping it shallow, and plants are either column feeders, or in the case of some crypts, they're in small dirted, cravel-capped bowls.
I'm interested in your cory thoughts wraithen, I've had very mixed results myself. This is my second time losing a batch of sterbai, the first was a completely different tank and situation over 6 months ago. Hmmm.
At the same time, I just bought 5 panda cories from a local big als for a tank I keep at my parents' place, and they seem to be doing happy and well. Grrr.
I'm thinking I'll get a few bronze cories, which are generally cheaper hereabouts, and do a trial run with them, sort of trouble shooting.
Tank is kept at 80F.

Ok. 80 should have been fine. That shallow of sand has pretty much no chance of developing dangerous levels of anything.

My thoughts on the sterbais lately is we all want them. A few of my local petco and petsmarts literally can not get them into their tanks. People are waiting at fish shipment days and buying them up on the spot. They are in great demand lately so I'm guessing corners are being cut with the operations, or the breeding isn't being done very well. Idk. Whatever the case, a lot of people are having a crazy time with them so it turned me off. I love cories, but they are not lucky, for me at least.

 

Anyone else have 2c they want to share? How so much gas can build up, seemingly so quickly in their gut?
I hate to call folks out by name, but was hoping to hear from DoubleDutch , any other cory experts?
Minnowette I am always interested to hear your take, or your sharing of what Noga has to say on the matter (I looked that resource up on amazon books, OMG I’ll never be buying that, so am grateful to you for having read it and sharing contents).

 

What did you feed them ?

 

DoubleDutch I didn't record daily feedings (had I known it would end up this way, I might have), but I know it included a couple of HikarI sinking wafers...

and Fluval Bug Bites Bottom Feeders.

Also a tiny amount of ground flake food, since there are half a dozen pentazona barbs in the same tank.
Thanks!

Update: the lone sterbaI that survived this incident is still with us. It happily ate some thawed mini-bloodworms last night, while in a specimen container for observation. After that feeding, I returned it to the main tank. I know fish aren't disposable, but I kinda need to know if this tank is going to cause the same response every time I introduce bottom feeders.

 

Maybe they didn't like the bug bites?

 

Maybe they didn't like the bug bites?

I've only heard good things about them, and my own experience has been positive. My kuhlis in another tank love them (at least the few bites that get past the rummies LOL).
At this stage, it's a possibility? [that they didn't like them]

 

Oh I don't know, I'm just suggestion ideas. Were they bloated or stingy poo? it seems like cory cats can eat anything and everything, but if the intestines were in bad shape, it tells me that either the substrate needs to be stirred more, or the food was spoiled or not agreeing with them..... Just ideas.

I actually prefer to buy fish from pet store wholesalers, like petsmart or Petco, chain stores. I don't like Mom and pop stores, or buying from other aquariust. I believe that at least the chain stores buy from real ornamental fish farms, and all these farms have quality- control people and veternarians and they regularly test dead fish and keep disease under control. A hobbyist has less knowledge as a whole then the professionals because they do it for a living, and or went to college for it..... and they HAVE to sell healthy fish, or they won't be in business very long.

 

I have been thinking about this thread. I'm thinking the bloating or gas filled stomach could be post mortem since most animals start to bloat almost immediately after death.

 

Oh I don't know, I'm just suggestion ideas. Were they bloated or stingy poo? it seems like cory cats can eat anything and everything, but if the intestines were in bad shape, it tells me that either the substrate needs to be stirred more, or the food was spoiled or not agreeing with them..... Just ideas

Appreciated, and keep 'em coming!!
The HikarI pellets were brand new, the bug bites are easily 6 months old (but since it's dried, I don't see that as maybe a freshness issue, but not a spoilage issue).

I actually prefer to buy fish from pet store wholesalers, like petsmart or Petco, chain stores. I don't like Mom and pop stores, or buying from other aquariust. I believe that at least the chain stores buy from real ornamental fish farms, and all these farms have quality- control people and veternarians and they regularly test dead fish and keep disease under control. A hobbyist has less knowledge as a whole then the professionals because they do it for a living, and or went to college for it..... and they HAVE to sell healthy fish, or they won't be in business very long.

These fish came to me via a local aquarist, who had bought them from a wholesaler 6 weeks earlier. He has an arrangement with them that he can buy direct, where they don't normally sell to the public. So a little from column A, a little from column B.

I have been thinking about this thread. I'm thinking the bloating or gas filled stomach could be post mortem since most animals start to bloat almost immediately after death.

I've experienced that too (floating post-mortem), but these guys started floating while still alive and kicking (1/4 deaths I'm not sure, cause it was dead/floating when I came home, but for the other 3/4, they remained alive for hours after they bloated/floated.

 

I don't think it was the food. Possible swim bladder issue, but that's a symptom, not a cause.

 

I don't think it was the food. Possible swim bladder issue, but that's a symptom, not a cause.

While I can't rule out a swim bladder issue, I do know that the stomach/intestines were full of air. I also tend to agree that it was probably not bad food that caused gassy guts. But I'm unable to offer a firm alternative. Are there any gut bacteria which, if reproducing at pathogenic levels, produce gas as a byproduct of their metabolism? Ie could it just be an unbalanced gut fauna?

 

Allmost sounds like selfpoissoning.

 

Allmost sounds like selfpoissoning.

While this is possible, its not plausible in a normal tank setting. Theres a lot of water to dilute the toxin. Probably the best direction weve come up with thus far though.

 

While this is possible, its not plausible in a normal tank setting. Theres a lot of water to dilute the toxin. Probably the best direction weve come up with thus far though.

I know and agree for the fullest. Puzzled by what happened though so many dieing at the same time.

 

I'm greatly appreciative of the discussion.
I never expected a firm solution. Sometimes it's good just to bounce thoughts and ideas off others (esp those with more/broader experience), just to see if I'm missing something, or looking at something the wrong way.
I did take some pics of the autopsies last week, and I'll post them later tonight.

Edit: follow up question about the toxin issue. Does it affect other species of fish?

 

I'm greatly appreciative of the discussion.
I never expected a firm solution. Sometimes it's good just to bounce thoughts and ideas off others (esp those with more/broader experience), just to see if I'm missing something, or looking at something the wrong way.
I did take some pics of the autopsies last week, and I'll post them later tonight.

Edit: follow up question about the toxin issue. Does it affect other species of fish?

It would affect anything that absorbed it

 

Some pics showing ventral view, and air in intestines. Some food bits also evident.







One of the sterbaI had a red lesion or mark on one side (behind pec fins, so not gill-related). There was no indication of trauma on the inside of the abdominal cavity, or obvious cut or wound.



Here’s a pic of one of them floating on its side at the surface (same one as above, before death).

 

Thanks for doing what you're doing! So I looked up those barbs. Man, can they live in some low ph water!

Unless they were being targeted hard core I still can't believe they would self poison in a tank. Cories are usually oblivious to harrassment in tanks anyway.

You mentioned you were trying to lower your ph. Aside from the tiny amount of humic acid and decaying matter in the tank, is there anything else you're trying?

 

Thanks for doing what you're doing! So I looked up those barbs. Man, can they live in some low ph water!

Unless they were being targeted hard core I still can't believe they would self poison in a tank. Cories are usually oblivious to harrassment in tanks anyway.

You mentioned you were trying to lower your ph. Aside from the tiny amount of humic acid and decaying matter in the tank, is there anything else you're trying?

uhhhh trying to lowering Ph ?????

 

uhhhh trying to lowering Ph ?????

Sorry, meant trying to lower the hardness. I assumed that would affect the ph also since its hard to isolate only what affects gh and not kh.

 

Sorry, meant trying to lower the hardness. I assumed that would affect the ph also since its hard to isolate only what affects gh and not kh.

First thing that jumped to mind when I saw the first post was an osmotic issue. Not air but fluid "sucked in" the fish .

Made no sense at that time and missed the attemps to lower hardness.

 

Sounds to me there were some health problems before you got them. If only 5 of the 13 lived I would think something happened to them prior to you getting them. Maybe something got in the past tank and you got them but it was just to late to help them? Or some sort of inherited problem in the group?

Self poisoning isn't a common thing so I really doubt it would be that, and if it were they can swim away from it and there would be enough water to dilute it. I really don't know, just guessing. I think they have to be REALLY stressed by being attacked or something like that to actually self poison. Again, I'm guessing by what research I've done on line about it. So I may be way off, just my thinking.

All the cory cats I have had have always been one of the toughest fish I've owned. I know I didn't help much but I am interested in the outcome, will be following.

 

I heard that sterbais are more sensitive than other cories. Sorry about your loss. In your first email you write that nitrites and nitrates are low. Nitrites need to be zero especially for sensitive fish.

Don't keep panda cories in 80F warm water. They need cooler temperatures. planet catfish is a great ressource.

 

Sounds to me there were some health problems before you got them. If only 5 of the 13 lived I would think something happened to them prior to you getting them. Maybe something got in the past tank and you got them but it was just to late to help them? Or some sort of inherited problem in the group?

Self poisoning isn't a common thing so I really doubt it would be that, and if it were they can swim away from it and there would be enough water to dilute it. I really don't know, just guessing. I think they have to be REALLY stressed by being attacked or something like that to actually self poison. Again, I'm guessing by what research I've done on line about it. So I may be way off, just my thinking.

All the cory cats I have had have always been one of the toughest fish I've owned. I know I didn't help much but I am interested in the outcome, will be following.

Fully agree with you Annie. It is very unlikely (I meand during transport though).
The fish look in great shape, so I dout there were healthissues before.

Must be something in the water and/or difference in ph/hardness/tds causing a shock.

Really puzzles me.

I heard that sterbais are more sensitive than other cories. Sorry about your loss. In your first email you write that nitrites and nitrates are low. Nitrites need to be zero especially for sensitive fish.

Don't keep panda cories in 80F warm water. They need cooler temperatures. planet catfish is a great ressource.

correct x 2

 

Thanks all for your interest/review and comments.

In your first email you write that nitrites and nitrates are low. Nitrites need to be zero especially for sensitive fish.

If I was unclear in my language, sorry. I meant to write that ammonia and nitrites are zero, and nitrates are low (under 10ppm, before pwc).

uhhhh trying to lowering Ph ?????

I have driftwood, IAL and alder cones in the tank, and add about 0.5mL humic acid per 10 gallon water. I've only just started using it, still being very conservative in my amounts. I literally just tested pH and hardness last night (just got GH/KH kit yesterday!).
pH in this tank is currently around 7.5, GH 7, KH 3. I am also gradually introducing a greater percentage of RO (through pwc's),with the goal of eventually having all remineralized RO. My tap water is incredibly well buffered, but is not far from these parameters. GH is 9, KH is 4. But the parameters are not swinging, I'm making these shifts very gradually. And despite the water being well stained with tannins from the IAL, alder cones, and humic acid, the parameters are still very close to my other tanks, which are basically conditioned tap water.

Don't keep panda cories in 80F warm water. They need cooler temperatures. planet catfish is a great ressource.

The pandas are in a separate tank, in a separate house. I mentioned then only as an irony complaint. I've bought and lost 2 batches of sterbai, 6 months apart, and can't seem to keep them around. I'm starting to take it a bit personally, and see this as a challenge. But I got 6 pandas for another tank that I don't even get to enjoy but once a week, and they're all doing great. sigh.

So mucy talk of this template lately, thought I'd try it out, retroactively:

Tank
How many gallons is your tank? 40 (breeder)
Does it have a filter? Cascade 700 plus 3 sponge filters.
Does it have a heater? Yes
What is the water temperature? 80F

Maintenance
How often do you change the water? Weekly
How much of the water do you change? 10 gal (25%)
What do you use to treat your water? Prime
Do you vacuum the substrate or just the water? Yes, vacuum.

Parameters
What do you use to test the water? API master kit, and dipsticks.
What are your parameters? We need the exact numbers, not just “fine” or “safe”.

Ammonia: 0
Nitrite: 0
Nitrate: <10
pH: 7.5

Feeding
How often do you feed your fish? Once/day
How much do you feed your fish? tiny pinch
What brand of food do you feed your fish? various. bug bites, hikarI wafers,
Do you feed frozen or freeze dried foods? frozen about 2x per week, choice of bloodworms, mysis, brine shrimp,

Symptoms
When did you first notice these symptoms? Friday 2nd Oct, 4pm
Have you started any treatment for the illness? 30 min epsom salt bath, then hospital tank for ~3d with Melafix. Now back in main tank.
Was your fish physically ill or injured upon purchase? complicated, see original post.
How has its behavior and appearance changed, if at all? also see original post, and subsequents.

First thing that jumped to mind when I saw the first post was an osmotic issue. Not air but fluid "sucked in" the fish .

Been thinking about this. The intestines were definitely filled with air not fluid.
Does properly acclimating new fish address this ootential issue, or does it exert an influence over a longer span (days, weeks)?

Sad update: I euthanized the final sterbaI half an hour ago. It was fine at 430 when I got home, but was floating and spiral-swimming an hour later. I did another super-fast dissection, and it’s intestines were again filled with air. No other symptoms. I didn’t feed it today.
It’s been 3 days since I returned it to the tank from the hospital tank. With the first round of deaths, it was 2 days from introduction to floating.
I find it odd that the gas/floating was very rapid onset both times, and occurred at the same time of day both times. Don’t know what to make of it though.

 

If you use sand as a substrate, I'm willing to be it was accumlated pockets of toxic gas that builds up from decaying matter in tanks with sand. You have to stir the sand, do it every time you change the water.

The OP's substrate probably isn't sand. It's "blasting sand" which now days is mostly coal slag, not actual sand. Still could hold pockets of gas. I wonder if said gas reacts with coal slag.