Hi all,

For a few weeks now, one of my zebra danios has been developing a swollen belly, and then more recently a black spot began to grow on its head, deepening in color and size over time. The weird thing is that it is behaving completely normal.

Any ideas on what this disease is and how to treat it?

Please see the picture - danios move so fast but I think you can get the gist of it.

I do see the black spot!.For the belly the fish could be femlae developing eggs.But Im at a loss on the black spot.Is it fuzzy or like a lump?or is it more like coloration?

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Thanks for your input!

I don't think it is pregnant because the swollen belly is lopsided, as in one side is bigger than the other. It also has been like that for quite some time.

The black spot is neither fuzzy nor a lump. It is simply the coloration - and potentially a little bit concave.

First thing that came into my mind was hole in the head disease, but that is usually on bigger fish and is fuzzy. As long as the fish is acting normal, I don't think it will do anything.

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10 gallon tank: 2 Tetra Whisper PF10 filters, mixed substrate, 1 male molly, 1 female platy,1 pregnant platy, 4 platy fry, 4 zebra danios
15 gallon tank: beaslbob build, peat moss substrate, pool sand substrate, 4 zebra danios, 10 neon tetras, 8 harlequin rasboras, 11 ghost shrimp, planted with: hornwort, anacharis, wisteria