Black Patches

[Polaris]

Hi all,

Several of my fish appear to be developing black patches. At first I thought these might just be natural changes in the colouration of the fish as they grow older (they are quite young fish) but as the onset has affected several fish simultaneously I am beginning to worry that there may be something more sinister going on.

I have researched the problem and don't believe that this is 'black ich' as the black patches are not small salt-grain type flecks on the body; instead they seem to be large bruise-like discolourations inside the body of the fish. I'm attaching some photographs in the hope that someone here might recognize the problem and tell me how to treat it. Two of the fish are female Swordtails and the black patches can be seen developing on their lower abdomens. The yellow fish is a female Molly and the black patch can be seen on the side of the fish, behind its gills.

I'm sorry for not posting details of the water parameters here at this time. I am about to perform a water change and will test the water parameters at the same time and post the results back here if anyone thinks this will help. However, for the moment I was more concerned with posting the pictures in the hope that someone might recognize the problem. I would add that I do perform weekly water changes and test the water each time. At the last test (about a week ago) the water parameters were perfectly normal.

I would be very grateful for any help with the diagnosis here.

Thank you.

 

[hillbilly]

The swordtails look quite normal. Do a google search on "gravid spot".

The Molly however looks like it may be a problem. Can you get a better picture?

 

[KittyKat]

The first and the last photos are gravid spots (the babies), the middle photo is stomach and other insides.

 

[Polaris]

Ah, the gravid spot! I must confess that never occurred to me. However, I thought that was only visible on fish that were pregnant. These Swordtails can't be pregnant. They were born in my tank, but unfortunately their father died whilst they were still very small fry. Since then there have been no other male Swordtails in there. However, there have been some male Platys in there, and I believe they are capable of cross-breeding with Swordtails? Come to think of it, these Swords seem to get chased around by some male Guppies I have in there, but surely that's stretching it a bit to have cross-breeding between Guppies and Swords!

Hmmmm! Anyway, not too worried about the Swords after the reassurance received here.

As for the Molly, the 'bruising' seems to have only developed in the past few weeks. It wasn't always there. It also seems more pronounced on the right side than the left. Other than that though, she seems healthy and active in all other respects. Maybe it's nothing to worry about.

Thanks for the advice, and Merry Christmas!

 

[KittyKat]

Don't get too excited, that could very well just be non-fertilised eggs!