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georgep56 georgep56
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  • Posted on: 21/10/2018 9:20
Re: Losing corydoras :-( #1
Thank you so much for your help and advice.
As I kind of expected the remaining panda was hiding under a stone this morning. When I moved the stone it clearly wasn't at all well, so for the benefit of the other fish I have euthenised it
I have also now done another clean of the gravel and changed 25% of the water. I think I just need to be more conscientious with my cleaning and regularly move the rocks and wood to clean underneath.
Fingers crossed that the remaining fish are OK.
Thanks again,

georgep56 georgep56
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  • Posted on: 20/10/2018 18:07
Re: Losing corydoras :-( #2

Fishlady wrote:
There's nothing obvious from what you've said, except that 0 nitrate rings alarm bells. As the final product of the cycle, it's almost impossible to have 0 nitrates in a stocked tank. That may indicate that the cycle failed recently and produced ammonia and/or nitrite spike which killed the fish.


The 'zero' reading for nitrates is probably not 100% correct - our API Nitrate test kit has colour bands where yellow is zero and the next slightly orange band is 5ppm. The last test (taken soon after a regular 20% water change) was nearer to zero than to 5ppm, hence I put zero in my last post.

My wife has just been reading an article online which has made me think ... the tank has a lot of plants, wood and stones, which is a good habitat for the fish but makes it an absolute pain to clean the gravel. A week or so ago I did a 'deep clean' - moving all the stones and wood and cleaning all the gravel, which stirred up quite a bit of debris which the cories, by their nature, were foraging amongst. Do you think that it's possible that they have been 'poisoned' by being exposed to this debris? Should I be being more meticulous with cleaning the gravel? I have read elsewhere that having a build up of bacteria in the gravel as well as the filter is beneficial?

We've also been considering (prior to this disruption) fitting an external filter in place of the standard Fluval internal unit which has served us well since we bought the tank; obviously that won't make cleaning the gravel any easier but would you consider it a worthwhile upgrade? Would having an an external filter make the tank any "healthier" than an internal?

Thanks again!

georgep56 georgep56
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  • Posted on: 20/10/2018 15:15
Re: Losing corydoras :-( #3
Hi, and thanks for the speedy reply.

Test results:
Ammonia: 0ppm Nitrate: 0ppm Nitrite: less than 0.3mg/l
Tap water is slightly hard
Temperature: ~24'C

We took out one Panda Cory weeks ago which had damage to its tail fin, as we didn't want to risk any potential problems spreading to the other fish. We’re not sure whether it was fin rot or nibbled by other fish, though we haven’t added any new fish for a bit, and it’s a community tank, so we don’t tend to have nipping problems. We have noticed that occasionally shrimps will 'pester' the cories as they lie 'asleep' on the bottom of the tank, sitting on top of them and appearing to 'nibble' at them until the cory 'wakes up' and swims away. I've taken another photo of the remaining 'poorly' cory as I'm not at all sure that the dorsal fin looks right?

We haven't noticed any damaged barbels. We realise that gravel isn't ideal for cories but we've had them in the same situation for as long as we've had the tank (>5 years).

It seems odd that all of the the panda cories and two pepper cories have died within days of each other, yet the albinos are fine - touch wood!

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georgep56 georgep56
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  • Posted on: 20/10/2018 9:21
Losing corydoras :-( #4
Hi all,

Over the last number of days a number (2-3) of our peppered and panda corydoras have died, and this morning another one is lying very lethargic at the bottom of the tank, alive but only just

All of the other fish in our well-established 120l tank (various barbs and tetras, albino corys, shrimps...) appear to be fine and active, the water tests (ammonia, nitrate, nitrite) are all spot on (I have been doing regular water changes).

It appears that *something* is affecting just the corys. The ones that have died have had no visible marks or scars anywhere and no other effects such as bloating and the 'only just alive' one, apart from having its fins closed down, appears visibly OK. I am attaching a photo.

If anyone could suggest anything I'd be really grateful; the only thing that comes to my mind, having racked my brains, is the slight possibly of overfeeding, but nothing as changed and why would only the corys be affected?

Thanks in anticipation!

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georgep56 georgep56
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  • Posted on: 15/6/2018 14:26
Re: Fish dying - no apparent reason? #5
Thanks @fishlady for the reply - much appreciated.
I'm already doing regular testing and water changes so I'll just keep doing more of the same and fingers crossed it will all settle down soon.

georgep56 georgep56
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  • Posted on: 14/6/2018 9:48
Fish dying - no apparent reason? #6
Hi everyone.

I've just signed up to the forum and hope someone can help.

We have a Fluval 120 litre tank with internal filter that has been running happily for several years with a variety of community fish - platys, corys, barbs, tetras, shrimps and snails. There are also 2 or 3 'real' plants, all well-established.

We have never overstocked the tank, have regularly changed the water and we regularly test the water and nothing has ever gone outside of the normal parameters. It is at least a couple of years now since we used any medications, we just use 'tap safe' when changing the water and occasionally add stress coat.

Over the last couple of months we have lost an unusual number of fish with no pattern to those that have died. There have probably been 6 or 8 fish in total, they have shown no signs of any illness or disease, they have simply been found dead (and half-eaten!) - usually in the morning.

One thing that did happen some weeks ago is that a large trumpet snail was left dead and unnoticed and when it was removed the stench of decay from the snail shell was awful. Having found this I thought that I'd found the cause of our mysterious deaths. I immediately did a 25% water change and did the same over the next couple of days.

This was a couple of weeks ago now and since that event we thought the tank was settling down, then this morning there was another dead peppered cory in the tank.

* Could the dead and decaying snail have caused the series of mysterious deaths over several weeks?

* Is there anything apart from extra water changes and regular testing / monitoring that I can do to try to avoid more deaths?

* Should I add any more fish (say something resilient such as Danios) or just wait (and if so - for how long?) for things to [hopefully] stabilise?

Thanks in anticipation for any help or advice.
Somerset, UK