Sudden tank deaths

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larochem595

Aquarium Advice Activist
Joined
Oct 29, 2014
Messages
149
I am at a loss here.
This is the third loss in my tank. I have no idea what is going on. Water parameters look pretty darn good and stable. No ammonia, no nitrites and nitrates look to be around 5.
This is my second Cory to go in this exact manner- acting normal, combing the substrate and suddenly dead. When I left the house for work, she was happily combing the substrate doing normal Cory stuff. No signs of bloating or distress. Then I came home to a dead fish.
After my last loss, I had added a second Cory to the tank. It's a 10 g tank with three otos and had two cories. (Now just one small one.)
I am doing an immediate water change tonight.

Ugh ??. This is so sad ...
 
Pictures of the dead and live fish, and a picture showing the entire tank?

How long has the tank been set up for?
How long have you had the fish for?
Have you added anything in the last 2 weeks?
What did you do to the tank yesterday?

What sort of substrate is in the tank?
Do you add anything to the tank (fertiliser, CO2, supplements, pH buffers, etc)?

Do you have perfume, moisturising cream, hand sanitiser, grease, soap, oil or anything else on your hands that might wash off into the water?

Do you have buckets specifically for the fish tank?

What sort of filter is on the tank?
How often and how do you clean the filter?

How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
 
This tank has been going about 7 years.
The Cory that died today has been in my tank about a year and a half ish. The otos were added at Christmas time. I very recently added a new Cory to replace the tank mate that died a couple weeks ago.
I did nothing to the tank yesterday other than add a scant amount of flake food.
I have gravel substrate.
Its a 10 g and I usually replace 2 gallons at a time. I add Prime, 2 mL of Replenish, and a pinch of equal parts Seachem alkaline and acid buffers (my city's water tends to be low in GH and kh.)
Yes, my buckets are tank dedicated.
I have a Whisper 20 hang on back filter. I typically rinse it in used tank water and stick it back in.

I tried to add a link to walk around of my tank.... hopefully it works.

Thank you!!



https://youtu.be/3Kf_GAuAHiA



Pictures of the dead and live fish, and a picture showing the entire tank?

How long has the tank been set up for?
How long have you had the fish for?
Have you added anything in the last 2 weeks?
What did you do to the tank yesterday?

What sort of substrate is in the tank?
Do you add anything to the tank (fertiliser, CO2, supplements, pH buffers, etc)?

Do you have perfume, moisturising cream, hand sanitiser, grease, soap, oil or anything else on your hands that might wash off into the water?

Do you have buckets specifically for the fish tank?

What sort of filter is on the tank?
How often and how do you clean the filter?

How often do you do water changes and how much do you change?
Do you gravel clean the substrate when you do a water change?
Do you dechlorinate the new water before adding it to the tank?
 

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Additional info--these deaths were very sudden.
The one thing I have observed is heavy gill pumping.
The small Cory that I have left is doing some darting.
I don't think it's a cycling issue.
 
This tank has been going about 7 years.
The Cory that died today has been in my tank about a year and a half ish. The otos were added at Christmas time. I very recently added a new Cory to replace the tank mate that died a couple weeks ago.
I did nothing to the tank yesterday other than add a scant amount of flake food.
I have gravel substrate.
Its a 10 g and I usually replace 2 gallons at a time. I add Prime, 2 mL of Replenish, and a pinch of equal parts Seachem alkaline and acid buffers (my city's water tends to be low in GH and kh.)
Yes, my buckets are tank dedicated.
I have a Whisper 20 hang on back filter. I typically rinse it in used tank water and stick it back in.

I tried to add a link to walk around of my tank.... hopefully it works.

Thank you!!



https://youtu.be/3Kf_GAuAHiA

Do you adjust your water before adding it to the tank or do you add the buffers directly into the tank?
 
Do you adjust your water before adding it to the tank or do you add the buffers directly into the tank?

I let my water rest overnight, put my water additives in the fresh water bucket, mix it up a bit, do my vacuuming into my designated dirty water bucket, then put my fresh water in.

In sum, yes, I adjust my water before adding it to the tank.
 
I let my water rest overnight, put my water additives in the fresh water bucket, mix it up a bit, do my vacuuming into my designated dirty water bucket, then put my fresh water in.

In sum, yes, I adjust my water before adding it to the tank.

Okay, that's good. (y)
Since whatever this is is only effecting these 2 cories, it stands to reason that the issue is a Cory thing and not necessarily a tank thing. Heavy gill pumping is a sign of a few disease issues but since these fish have been in the tank for over a year, it's unlikely to be disease. That your surviving cory is " darting" sounds like there is a water element that is not to their liking. That your fish died after a water change sounds like there was too drastic a change in the water parameters when you changed water. Did you test your tank water prior to changing it and did you test the replacement water to make sure it was okay to add before adding it? ( Rapid Ph change can cause corydora catfish to dart around.)
 
Okay, that's good. (y)
Since whatever this is is only effecting these 2 cories, it stands to reason that the issue is a Cory thing and not necessarily a tank thing. Heavy gill pumping is a sign of a few disease issues but since these fish have been in the tank for over a year, it's unlikely to be disease. That your surviving cory is " darting" sounds like there is a water element that is not to their liking. That your fish died after a water change sounds like there was too drastic a change in the water parameters when you changed water. Did you test your tank water prior to changing it and did you test the replacement water to make sure it was okay to add before adding it? ( Rapid Ph change can cause corydora catfish to dart around.)

So, my last water change was about 5 or so days ago--either Friday or Saturday. The small Cory was darting since I got home and the fish that died was before the water change. (I did the water change in response to my fish dying.)
I am tending to agree that the cories are being affected much more , as they have been dying one by one. My otos seem less affected. Although, one of them looked a little reddish to me (the second one in my video clip.)

I am waiting on a new GH/KH test kit-unfortunately, mine expired and the GH test was all clumpy and I didn't trust it....there were none locally available and I ordered a new one online. When it comes in, I will do a good study of everything.
I will do another water change/vacuuming tomorrow. If anyone can think of anything else I should be doing, keep me posted....thanks for the help. ��
 
So, my last water change was about 5 or so days ago--either Friday or Saturday. The small Cory was darting since I got home so I am not sure when that started but it was before the water change.
I am tending to agree that this looks somewhat species-specific, as the cories have been dying one by one. My otos seem less affected. Although, one of them looked a little reddish to me (the second one in my video clip.)

I am waiting on a new GH/KH test kit-unfortunately, mine expired and the GH test was all clumpy and I didn't trust it....there were none locally available and I ordered a new one online. When it comes in, I will do a good study of everything.
If anyone can think of anything else I should be doing, keep me posted....thanks for the help. ?
There is the possibility that the cories were fighting with each other and the stress was too much for the older one ( possibly a female) and she may have stabbed the smaller one ( possibly a male) and this is a reaction to the venom? Are these two of the same specie catfish?
Another possibility is that you opened a gas pocket from anaerobic bacteria when you cleaned the gravel last. Redness is a sign of poisoning and since these fish tend to be on the bottom, they would be the first fish to be effected. :confused:

In reality the only cory cats suitable for a 10 gal tank are the dwarfs/pigmy species: C. hastatus , C. pygmaeus and that is really pushing it. Even they should be in a school and in a larger tank with good water circulation.
 
There is the possibility that the cories were fighting with each other and the stress was too much for the older one ( possibly a female) and she may have stabbed the smaller one ( possibly a male) and this is a reaction to the venom? Are these two of the same specie catfish?
Another possibility is that you opened a gas pocket from anaerobic bacteria when you cleaned the gravel last. Redness is a sign of poisoning and since these fish tend to be on the bottom, they would be the first fish to be effected. :confused:

In reality the only cory cats suitable for a 10 gal tank are the dwarfs/pigmy species: C. hastatus , C. pygmaeus and that is really pushing it. Even they should be in a school and in a larger tank with good water circulation.

I definitely agree with you... knowing that they prefer to be in groups, I would have done more research and not gone with cories in a 10 g. Now I am stuck with this little guy... In good conscience, I wouldn't bring him back, just in case he does have something infectious. I also feel bad about keeping a Cory by itself.... I feel like I should have known better =(
 
This has nothing to do with the Corydoras but you need algae, biofilm and driftwood in the tank for the Otocinclus catfish otherwise they will starve to death. If you leave the aquarium light on for 8-10 hours a day you should get some algae growing on the glass and plants. Driftwood can be bought from pet shops. Biofilm is the clear slime on the inside of the tank on the glass and ornaments. When you clean the tank, wipe the front glass down but leave the back and sides. If they get too gross for you, then wipe one down and wait a few weeks before doing another side, wait a few more weeks before doing the back. But try to leave the back glass to get covered in algae and biofilm.

Having some live plants in the tank wouldn't hurt either. They can remove some nutrients from water and help keep things cleaner.

-----------------

Unless you're keeping hardwater fishes and you have very soft water, there is no need to add the Seachem alkalinity buffer. Corydoras and Otocinclus naturally occur in soft acid water with a very low mineral content. They don't need many minerals in the water.

If you are adding anything to adjust the pH, GH or KH, you should add it to a bucket of water and aerate it for 24 hours before using it in an aquarium with livestock. You should also check the water before adding it to the tank to ensure the pH, GH & KH are where they should be. If they aren't at the desired levels, add more buffer or dilute the bucket of water with some clean water and aerate for another 24 hours, then re-test. Some buffers can continue changing the water many hours later, so you need to aerate the solution for 24 hours to get a more accurate reading.

The Corydoras could do with some hiding places and a piece of driftwood would provide them with cover. A piece could be rested on the 2 rocks you have in the tank and the fish could hide under that during the day and the Otocinclus could graze on it. You can also use clay flower pots, or rocks that don't affect the water chemistry.

-----------------

In the video, the Corydoras is glass surfing and that is fine. However, the Otocinclus on the front glass has very red gills and that could be poisoning from something in the water or gill flukes or gill fungus. It's usually a water quality issue (ammonia, nitrite, nitrate) but can also be from heavy metal poisoning or other hazardous things that dissolve in water. The fact a Corydoras was fine and well in the morning and dead in the evening with no apparent signs of disease, and the water quality was good, might suggest you have something in the water supply that is poisoning the fish.

Perhaps add some carbon to the filter and see how things go over the next couple of months. You will need to replace the carbon every few weeks, depending on how much you use and whether it's in a carbon pad or just a bag of loose carbon granules. The bag of loose carbon granules will last longer than a carbon pad/ cartridge.

You can filter the tap water through carbon before adding it to the tank. This is the preferred thing to do because you aren't adding potentially contaminated water to the tank, then trying to filter it out. You would either run the tap water through a high grade carbon filter, or put a carbon filter in a bucket of tap water and let it run for a couple of days.

-----------------

I would find out exactly what the pH, GH and KH of the water supply is.

I would stop adding the alkalinity buffer.

I would filter the tap water through carbon before using it in the aquarium.

I would add some driftwood and maybe a few live plants.

You could also contact your water supply company via website and get a list of what is in the water. Then post it here. We might be able to find something that shouldn't be in there and that might be contributing to this.
 
Hi Colin,
Thanks for the long and thoughtful response.

So, I am pretty good with keeping otos...The tank has plenty of biofilm. I run the light whenever I am home. I supplement with algae tabs, which they seem to like. I have had good luck with my otos. (I managed to breed them by accident once ?. There's actually pictures of the fry in an old post.) My last one lived 6.5 years, which I would consider a good lifespan.

It's interesting to also note that my plants have also all died off. My Java ferns died off in the fall and my hornwort is losing all it's needles. It's almost gone too.

The idea that there could be heavy metals or something in the water is plausible. I moved to an older apartment home about 2 years ago. (I think built around 1900 ish) and there's a possibility of older piping. I will try pre-aerating and filtering my water. I have an old pump and filter I can use.

Gill flukes or fungus could also be plausible too, with the addition of new fish.

Thank you for the help, it is much appreciated ?. I just want to do right by my fish....

This has nothing to do with the Corydoras but you need algae, biofilm and driftwood in the tank for the Otocinclus catfish otherwise they will starve to death. If you leave the aquarium light on for 8-10 hours a day you should get some algae growing on the glass and plants. Driftwood can be bought from pet shops. Biofilm is the clear slime on the inside of the tank on the glass and ornaments. When you clean the tank, wipe the front glass down but leave the back and sides. If they get too gross for you, then wipe one down and wait a few weeks before doing another side, wait a few more weeks before doing the back. But try to leave the back glass to get covered in algae and biofilm.

Having some live plants in the tank wouldn't hurt either. They can remove some nutrients from water and help keep things cleaner.

-----------------

Unless you're keeping hardwater fishes and you have very soft water, there is no need to add the Seachem alkalinity buffer. Corydoras and Otocinclus naturally occur in soft acid water with a very low mineral content. They don't need many minerals in the water.

If you are adding anything to adjust the pH, GH or KH, you should add it to a bucket of water and aerate it for 24 hours before using it in an aquarium with livestock. You should also check the water before adding it to the tank to ensure the pH, GH & KH are where they should be. If they aren't at the desired levels, add more buffer or dilute the bucket of water with some clean water and aerate for another 24 hours, then re-test. Some buffers can continue changing the water many hours later, so you need to aerate the solution for 24 hours to get a more accurate reading.

The Corydoras could do with some hiding places and a piece of driftwood would provide them with cover. A piece could be rested on the 2 rocks you have in the tank and the fish could hide under that during the day and the Otocinclus could graze on it. You can also use clay flower pots, or rocks that don't affect the water chemistry.

-----------------

In the video, the Corydoras is glass surfing and that is fine. However, the Otocinclus on the front glass has very red gills and that could be poisoning from something in the water or gill flukes or gill fungus. It's usually a water quality issue (ammonia, nitrite, nitrate) but can also be from heavy metal poisoning or other hazardous things that dissolve in water. The fact a Corydoras was fine and well in the morning and dead in the evening with no apparent signs of disease, and the water quality was good, might suggest you have something in the water supply that is poisoning the fish.

Perhaps add some carbon to the filter and see how things go over the next couple of months. You will need to replace the carbon every few weeks, depending on how much you use and whether it's in a carbon pad or just a bag of loose carbon granules. The bag of loose carbon granules will last longer than a carbon pad/ cartridge.

You can filter the tap water through carbon before adding it to the tank. This is the preferred thing to do because you aren't adding potentially contaminated water to the tank, then trying to filter it out. You would either run the tap water through a high grade carbon filter, or put a carbon filter in a bucket of tap water and let it run for a couple of days.

-----------------

I would find out exactly what the pH, GH and KH of the water supply is.

I would stop adding the alkalinity buffer.

I would filter the tap water through carbon before using it in the aquarium.

I would add some driftwood and maybe a few live plants.

You could also contact your water supply company via website and get a list of what is in the water. Then post it here. We might be able to find something that shouldn't be in there and that might be contributing to this.
 
The reports are from 2021 and before so the water might have changed a bit since then. There are a couple of things that concern me.
Foam for fire fighting (from 2019)
Benzo(a)pyrene

There's a lot of substances from the chlorine reacting with organics in the water and that can be an issue in itself, but also means there's a lot of organic matter in the water.

The fact there was chemicals from fire fighting back in 2019, means there could be other chemicals that have gotten into the water supply too and just haven't showed up on tests or been tested for. There are lots of new chemicals being made accidentally in natural waterways and this is caused by things getting poured down drains and sinks and reacting with each other in the wild. There have been over 100 new chemicals found in the ocean caused by this.

I have found bottles of herbicide and pesticide in waterways down south that were miles from anywhere so people do dump things into waterways when they aren't meant to.

You could get a company to test your home tap water for everything and that should tell you exactly what is in it at that time. However, that can be expensive.

A reverse osmosis (r/o) unit would clean most things out of the water but so will carbon, and carbon is cheaper. Most r/o units have a carbon filter in them.

Try filtering the new water through carbon and see if it helps. Do this for a few months and see if any more fish die. If more fish do die, then post pictures immediately and provide a description of what happened (symptoms, etc). If the fish are fine then you might need to continue using carbon and I would then get the water tested by an independent lab to try and find out what is in it. You might also want to filter the water you drink and that you use for family and pets (if you have other pets besides the fish).
 
Tank update --
So my lone remaining Cory doesn't look well...I don't expect it to last too long ? It's gills are inflamed and it looks pretty listless.

My GH KH test kit finally came in (I have no clue why these things are suddenly so hard to get, was backordered for a few weeks.)
My KH was rather low, not able to be detected. It was either 0 or 1. I will gradually add more buffer, see if I can at least get it to register. I think my city changed to an auxiliary water supply over the winter and some of my parameters changed on me...

As for the fish, I think that one of the newer fish I had gotten dragged an infection into the tank, which seems to primarily affect the cories. The otos seem to be faring better.
They're acrobatically cleaning the tank, doing typical stuff. I haven't lost any of the 3 otos.

Unfortunately, the antibiotics (doxycycline) didn't kick whatever it was. So, my plan is to let this run its course and start over ?.
 
Tank update --
So my lone remaining Cory doesn't look well...I don't expect it to last too long ? It's gills are inflamed and it looks pretty listless.

My GH KH test kit finally came in (I have no clue why these things are suddenly so hard to get, was backordered for a few weeks.)
My KH was rather low, not able to be detected. It was either 0 or 1. I will gradually add more buffer, see if I can at least get it to register. I think my city changed to an auxiliary water supply over the winter and some of my parameters changed on me...

As for the fish, I think that one of the newer fish I had gotten dragged an infection into the tank, which seems to primarily affect the cories. The otos seem to be faring better.
They're acrobatically cleaning the tank, doing typical stuff. I haven't lost any of the 3 otos.

Unfortunately, the antibiotics (doxycycline) didn't kick whatever it was. So, my plan is to let this run its course and start over ?.
One of the down sides of being a corydora is that most parasites have a stage where they are in the substrate so when they emerge, they go after the first fish they can find that can be receptive. Since cories are bottom fish, they get it close to being first. :(
This apparently is not a bacterial issue since Doxy treats both gram - and gram + bacteria but works best if the Ph of the water is high ( above 7.5). If there are no water issues, you might want to try API's General Cure or Paracleanse by Fritz if they are available where you are. These contain Metronidazole and Praziquantel which are effective against many parasites that effect the gills. (y)
 
One of the down sides of being a corydora is that most parasites have a stage where they are in the substrate so when they emerge, they go after the first fish they can find that can be receptive. Since cories are bottom fish, they get it close to being first. :(
This apparently is not a bacterial issue since Doxy treats both gram - and gram + bacteria but works best if the Ph of the water is high ( above 7.5). If there are no water issues, you might want to try API's General Cure or Paracleanse by Fritz if they are available where you are. These contain Metronidazole and Praziquantel which are effective against many parasites that effect the gills. (y)

Thanks, it's worth a shot....
I am assuming these won't mess with the cycling of my tank because they are parasite drugs??
 
Doxycycline is an antibiotic that wipes out filter bacteria and shouldn't be used in aquariums due to drug resistance in bacteria.

Metronidazole is an antibiotic that can be used to treat internal protozoan infections in fish. Internal protozoan infections cause the fish to go off its food a bit, lose weight over a couple of weeks and do a stringy white poop. If the fish is not showing any of these symptoms, then Metronidazole should not be added to an aquarium.

Praziquantel is a medication used to treat tapeworm in dogs and cats but also kills tapeworm in fish. It does not treat anything else. Tapeworm cause fish to lose weight over a period of months. The fish eat normally but can do a stringy white poop. If the fish is not losing weight, and doesn't do a stringy white poop, do not add Praziquantel to the tank.
 
Doxycycline is an antibiotic that wipes out filter bacteria and shouldn't be used in aquariums due to drug resistance in bacteria.

Metronidazole is an antibiotic that can be used to treat internal protozoan infections in fish. Internal protozoan infections cause the fish to go off its food a bit, lose weight over a couple of weeks and do a stringy white poop. If the fish is not showing any of these symptoms, then Metronidazole should not be added to an aquarium.

Praziquantel is a medication used to treat tapeworm in dogs and cats but also kills tapeworm in fish. It does not treat anything else. Tapeworm cause fish to lose weight over a period of months. The fish eat normally but can do a stringy white poop. If the fish is not losing weight, and doesn't do a stringy white poop, do not add Praziquantel to the tank.

Regarding praziquantel, this is from the site sciencedirect: The anthelmintic praziquantel (PZQ) can effectively treat a range of flatworm parasites in a variety of fish species and has potential for broader application than its current use in the global aquaculture industry.
 
Thanks, it's worth a shot....
I am assuming these won't mess with the cycling of my tank because they are parasite drugs??

Correct, it should not affect the bacteria bed.

As for Colin's response, I have posted this response to him: this is from the site sciencedirect" The anthelmintic praziquantel (PZQ) can effectively treat a range of flatworm parasites in a variety of fish species and has potential for broader application than its current use in the global aquaculture industry."

Since we do not know for sure what is affecting your fish, I would use it with the metronidazole. (y)
 
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