# CPD turning black...why?



## Fisheye (Jan 13, 2015)

*CPD turning black...why? **UPDATE from WetWebMedia*

Hi,

Just wondering if anyone knows what is going on with this fish. The black spot has been growing over time. Behaviour is normal and no other CPD's are affected.

I have tried to google this but haven't found any reference.

Would be interested to see what anyone thinks.

Thank you.

Jackie`

**Excellent reply from WetWebMedia on January 8, 2018

Black patches on aquarium fish tend to be caused by four different things. 
The first is ammonia burns, but I think we can discount those here. Check 
to see if there's any sign of white tissue (i.e., dead skin) or red/pink 
colouration (i.e., bacterial infection and congested blood vessels). Either 
of these can imply damage to the scales and skin. But in the absence of 
either, it's more likely the black colour is pigmentation rather than 
damage. The second cause of black colouration is some type of parasitic 
infection, sometimes called 'Black Spot Disease' and more commonly seen in 
ponds. For various reasons it's rare in aquaria and tends to die off after 
a while without causing any major issues, all else being equal. Again, I'd 
dismiss this possibility because your fish has a black patch, not lots of 
small spots. The third reason is genetics, the issue really being one about 
the quality, or otherwise, of the parent fish. In this situation you 
usually have, say, a golden-coloured morph or artificial form (like, for 
example, a Midas Cichlid or a Goldfish) with some darker coloured fish in 
its parentage. For whatever reason juveniles were golden, but some of those 
darker genes express themselves as the fish ages, and dark patches appear. 
Now, while it's possible the issue here is genetic, this species hasn't 
been line-bred yet, we're not really talking about a genetic 'throw-back' 
but rather a simple 'sport of nature' of those sort Darwin famously 
described. In other words, there's variety within populations, and 
mutations will sometimes present themselves as different colours, 
fin-lengths and so on. In the wild natural selection would work on them, 
favouring those that might be useful, or against such mutations that made 
the fish less successful. It's just possible we're talking about that here, 
and if the fish is otherwise healthy and happy, you've simply been lucky 
enough to watch "evolution in action", so to speak, with this fish having a 
mutation in colouration that sets it apart from all the other Celestial 
Pearl Danios / Galaxy Rasboras on the planet! Finally, there's a 
developmental issue or some type of physical damage that has caused the 
fish to turn black. One example is nerve damage (perhaps from a physical 
injury) that 'jams' the nerves that allow fish to change their colours at 
will, rather like a stuck pixel on an LCD screen. The result is that the 
colour pigment cells are stuck in black (or whatever colour) mode, and you 
see a fixed patch of abnormal colour. Developmental issues can also be 
caused by vitamin deficiencies and certain infections such as Fish TB, but 
your aquarium otherwise sounds excellent, so I'm somewhat skeptical of 
this. So my gut feeling, without evidence to the contrary, is that this is 
a healthy fish with a genetic abnormality, and provided he's happy doing 
his thing, I'd not be concerned. Whether or not you want to breed from him 
is another question, though that would, perhaps, allow you to determine if 
it is genetic or merely developmental. Cheers, Neale.


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## infolific (Apr 10, 2016)

That is strange. I tried to find something about it via Google and no luck either. Is there any texture to the patch? Is the black on the surface of the fish or underneath it?


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## Fisheye (Jan 13, 2015)

Thanks so much for your input and for doing a google snoop!

I wish I could answer your questions but it's such a quick and teeny fish that I can't discern much in detail. It's hard enough to get a picture without sitting in front of the tank for hours.

I've composed an email to wetwebmedia but wanted to see what folks on here thought. The CPD's were from ShrimpFever so if it was a genetic issue, I had hoped someone on the forum might have had a similar issue with stock from there.

And in no way am I suggesting this is anything to do with ShrimpFever stock.

Thanks again Infolific. I will post back if I learn anything definitive.

Jackie


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## infolific (Apr 10, 2016)

I was able to find other similar reports, but not CPD specific. I used a more general search: "my fish is turning black". Nothing definitive in the replies with folks citing the usual suspects of high ammonia, high nitrites, and bacterial infection.

I have several CPDs from ShrimpFever as well. I got them in March 2017. I lost one to something unknown, but the others are faring well.


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## Fisheye (Jan 13, 2015)

Hey,

Thank you your efforts. I cast a broad net on google too and also on WWM-came up with the same. Also saw reference to nerve issues due to trauma, which can't be ruled out. They do zip around when sparring and spawning. Just glad it's just the one!

Have yours spawned for you? Did you set up a biotope or what kind of home did you make? Is this considered thread hijacking? Does it matter if it's your own thread?

Thanks again.

J


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## infolific (Apr 10, 2016)

Fisheye said:


> Have yours spawned for you? Did you set up a biotope or what kind of home did you make? Is this considered thread hijacking? Does it matter if it's your own thread?


I haven't seen any eggs or fry, but I've seen a lot of what I consider to be spawning behaviour. I have a heavily planted tank (random collection of plants, not a biotope) and they're usually partially hidden when I observe this behaviour so I can't be sure that I just haven't seen the eggs.

It's only thread hijacking if the OP says it is


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