Corydoras

[AlexT]

Started losing colour in it's head about 3 to 4 days ago, was very noticeable, as the rest of his body was the usual dark colour. Over the past few days the loss of colour has extended. If you look closely, there is a pattern, almost like a straight line of colour loss. The pictures are not the best quality as I had to enlarge them due to the position he is in and my using my phone. He has lost more colour than the pictures portray. You would almost think he is dead, but he is moving around and active. He doesn't look especially skinny for his size.

I've had two other cory deaths in the past 2 weeks. Both times I found the corpse. One was of normal size and build but the other corpse was a skinny one I had noticed recently. I remember this one, as he was skinny when I got him about a month ago, but because he was small anyway (about 2cm) I didn't think too much of it, as the rest of the group from the LFS all looked great. I had purchased 8. With the deaths, I have 18 remaining.

I've not noticed any flashing or rubbing from any of the fish, apart from one corydoras, one time, a few days back.

The other fish (18 tetra and 4 small BN) all look great.

Water parameters are always nil for ammonia and nitrite, and 10-15 for nitrate. Temp 76F, pH 7.5, GH 6-7

 

[Aqua67]

Sounds like the fish is stressed. Here are some things to consider.

Does the cory have any other cories now to hang out with?

Is this cory eating and swimming around as would be normal (as opposed to just staying in one spot, not eating, etc.).

Is there another fish in the tank picking on this pale cory, one of your bristlenose perhaps (?). If they have paired off the males can be territorial and might be keeping the cory away from a spot it used to frequent. It may be getting “bullied”.

Is there enough hiding places for all of your bottom dwellers?

 

[AlexT]

Sounds like the fish is stressed. Here are some things to consider.

Does the cory have any other cories now to hang out with?

Is this cory eating and swimming around as would be normal (as opposed to just staying in one spot, not eating, etc.).

Is there another fish in the tank picking on this pale cory, one of your bristlenose perhaps (?). If they have paired off the males can be territorial and might be keeping the cory away from a spot it used to frequent. It may be getting “bullied”.

Is there enough hiding places for all of your bottom dwellers?

Thank you. None of those things are at play here, but they are good questions. There are 18 Bronze Corydoras. This Cory was eating 2 days ago when I last fed, and he was swimming as normal. I haven't been able to assess his movement properly yet today. He is either more lethargic or I haven't spent enough time looking. No fish are bothering the Corydoras. I have lots of driftwood, and it is heavily planted. There is good amounts of quiet places for the Cory to chill and be out of the light etc.

 

[AlexT]

I put in a bit more food than I normally would at a place the corydoras normally go to at feeding. I wanted to get a good view, under the lights of some of the other cory and I got a video of the one in question. He is looking for food and appearing to eat. His movement doesn't quite seem right, but I don't know if you can pick that up from the video.

 

[Byron]

@Colin_T will likely know what this is, I have I think had it but no idea, and it was years ago.

 

[AlexT]

Is it columnaris Colin?

 

[MuddyWaters]

I put in a bit more food than I normally would at a place the corydoras normally go to at feeding. I wanted to get a good view, under the lights of some of the other cory and I got a video of the one in question. He is looking for food and appearing to eat. His movement doesn't quite seem right, but I don't know if you can pick that up from the video.

his body looks bent in the middle and he's dragging his belly across the bottom rather than floating a bit above the gravel. I poked around a bit and saw someone suggest that maybe Neon Tetra disease has been transferred due to the cory eating a dead neon tetra?

 

[Colin_T]

Did the other catfish that died have the same symptoms (white body)?
If yes, how long did they live for with the white body?

It looks like a Microsporidian infection. It turns the muscle tissue cream/ white over a period of time (2 weeks - 2 months) and the fish eventually dies. They act normally during this time but the parasite is destroying the underlying muscle tissue.
It's highly contagious and is spread by other fish eating the diseased tissue.
Salt is the only thing I know that treats it.

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Wipe the inside of the glass down with a clean fish sponge. This removes the biofilm on the glass and the biofilm will contain lots of harmful bacteria, fungus, protozoans and various other microscopic life forms.

Do a 75% water change and gravel clean the substrate. The water change and gravel cleaning will reduce the number of disease organisms in the water and provide a cleaner environment for the fish to recover in.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

Clean the filter if it hasn't been done in the last 2 weeks. However, if the filter is less than 6 weeks old, do not clean it. Wash the filter materials/ media in a bucket of tank water and re-use the media. Tip the bucket of dirty water on the garden/ lawn. Cleaning the filter means less gunk and cleaner water with fewer pathogens so any medication (if needed) will work more effectively on the fish.

Increase surface turbulence/ aeration to maximise the dissolved oxygen in the water.

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SALT
You can add rock salt (often sold as aquarium salt), swimming pool salt, or any non iodised salt (sodium chloride) to the aquarium at the dose rate of 2 heaped tablespoon per 20 litres (5 gallons) of water.

Keep the salt level like this for at least 2 weeks but no longer than 4 weeks otherwise kidney damage can occur. Kidney damage is more likely to occur in fish from soft water (tetras, Corydoras, angelfish, Bettas & gouramis, loaches) that are exposed to high levels of salt for an extended period of time, and is not an issue with livebearers, rainbowfish or other salt tolerant species.

The salt will not affect the beneficial filter bacteria, fish, plants, shrimp or snails.

After you use salt and the fish have recovered, you do a 10% water change each day for a week using only fresh water that has been dechlorinated. Then do a 20% water change each day for a week. Then you can do bigger water changes after that. This dilutes the salt out of the tank slowly so it doesn't harm the fish.

If you do water changes while using salt, you need to treat the new water with salt before adding it to the tank. This will keep the salt level stable in the tank and minimise stress on the fish.

When you first add salt, add the salt to a small bucket of tank water and dissolve the salt. Then slowly pour the salt water into the tank near the filter outlet. Add the salt over a couple of minutes.

 

[AlexT]

his body looks bent in the middle and he's dragging his belly across the bottom rather than floating a bit above the gravel. I poked around a bit and saw someone suggest that maybe Neon Tetra disease has been transferred due to the cory eating a dead neon tetra?

Thanks, yes. I noticed that too about the dragging.

 

[AlexT]

Did the other catfish that died have the same symptoms (white body)?
If yes, how long did they live for with the white body?

Thanks Colin. The other dead cory's didn't have these symptoms.

 

[AlexT]

So it's not columnaris @Colin_T? Is the white/grey patches too uniform, and widespread for this? Is it still a decent possibility that the lack of colouration could be a stress reaction to worms or another internal issue? I have not seen him scratch once.

 

[Colin_T]

Columnaris infections on the body start on the dorsal side near the dorsal (top) fin and work their way down, and the fish usually stop eating and die within a few days of developing it.

It's not worms or an intestinal infection. Worms don't cause the fish to change colour. Fish don't eat normally when they have an intestinal infection.

Microsporidian infections are characterised by the muscle tissue under the skin turning cream/ white. There's no other diseases that do this.

 

[Aqua67]

Be careful about using salt with cories. They don’t tolerate salt well.