What is the problem

[SPACKlick]

Please Describe

1. What is making you think this fish is ill. You have not given any description of symptoms and in the images there is very little to see. Without the symptoms nobody can help diagnosis

2. Your tank and its parameters. Size, other inhabitants, filtration, substrate and plants Water quality (Ammonia, Nitrite, Nitrate; KH,GH,PH, temperature)

Fixed links

[Martinspuddle]

Fixed links

Thank you @SPACKlick

[saiwong]

Please Describe

1. What is making you think this fish is ill. You have not given any description of symptoms and in the images there is very little to see. Without the symptoms nobody can help diagnosis

There is a white-ish stuff around the top of the tail area. Also his head seems to take cracks or marks on it

2. Your tank and its parameters. Size, other inhabitants, filtration, substrate and plants Water quality (Ammonia, Nitrite, Nitrate; KH,GH,PH, temperature)

Fixed links

Ammonia 0
Nitrite 0
Nitrate 0 to 5
PH 7

Tank is 20 gallons

temp 76 to 78

Filters are hang on filter (no carbon) and a sponge filter

About 8 fish total in tank. Other fish Guppy and Platy fry & flying fox

Regular weekly water changes

Brought catfish about half year ago

Gravel substrait

[Martinspuddle]

As I previously said, mucus around the skull plates from stress.

Corydoras don't fair well on a gravel substrate. What are the other two Aeneus like?

[saiwong]

As I previously said, mucus around the skull plates from stress.

Corydoras don't fair well on a gravel substrate. What are the other two Aeneus like?

The other catfish are perfectly fine. Other fish in aquarium (guppy, platy etc ...) are fine also.

I am currently treating catfish with aquarium salt. Is this ok or would you recommend something else ?

[Martinspuddle]

As I previously said, mucus around the skull plates from stress.

Corydoras don't fair well on a gravel substrate. What are the other two Aeneus like?

The other catfish are perfectly fine. Other fish in aquarium (guppy, platy etc ...) are fine also.

I am currently treating catfish with aquarium salt. Is this ok or would you recommend something else ?

Be careful how much salt you use, not to higher dose.

Make sure the Corydoras are getting their fill at feeding time and have cover to stop any harassment from your Livebearers. Guppies and Platies can be a pain for pecking at stationary catfish.

[Vale!]

This is remarkable - in that I've not come across this before (not that that may be saying much!).

Has the fish always been like this (so far as you know) or has the condition appeared recently?

I'm struggling with the idea of skull plates influencing mucous production, irrespective of stressors. AFAIK skull plates are skeletal and are defined by sutures between developing bones ... nope - can't get my head around that at all! Maybe someone could steer me in the right direction.

My take (absent that explanation) assuming that it's not something that's developed suddenly :

Either the 'white-ish stuff' associated with the fish's peduncle (is that where you mean? and we haven't seen a decent pic of it) is linked to the weird effect on the head of the fish ; or it's coincidental.

If it's linked, then that could suggest (to me) a fungal infection over a bacterial one, given the mosaic-like pattern presented on the fish's skin.

If it's coincidental, then I favour a genetic origin : a chromosomal aberration affecting that individual during its early development. There is actually a condition known as "mosaicism". However my ambition to discover if and how it relates to fish skin has been thwarted by the fact that 'FISH' appears to be some kind of analytical tool in biology : any search string that I came up with resulted in references to that tool, and I don't have the skill to exclude them! [yes - I did try 'teleost'!]

At the moment my money's on a chromosomal anomaly.

[Martinspuddle]

This is remarkable - in that I've not come across this before (not that that may be saying much!).

I've seen this before with stressed Corydoras @Vale!. It's just a mucus that produces a pattern on the head, can also appear on the fins and scale plate edges from the excreted mucus.

Normally it disappears within a few days once the fish has settled. There use to be a paper online, I think from the University of Florida on Corydoras Sp. self poisoning and related stress. Unfortunately I can't find it.

They listed that a garlic bath would cure the self poisoning and related stress in Corydoras catfish.

@saiwong you could try garlic in their food or there some garlic treatments on the market.

[plankton]

...or just crushed, fresh garlic, left for 10 minutes and then dropped in the tank.
You only need about a quarter of a clove for the amount of fish you have.