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I'm thinking they may be C.arcuatus ????
I'm I right ?
They are wild fish any any help on breeding conditions ( sexing ) would help

Imo you are right:
When looking from above, males are more slender than females. Also the ventral fins (pointed versus rounded) should give the sexes away.
Apparently yours are large enough to see the differences. Very good looking specimens!

I miss something essential for Corys: sand. I take it they are in a Q-tank atm?

These are commonly known as "Super arcuatus" This fish is considered by many, me included, to be a separate species to C. arcuatus, which is a smaller fish having a deeper body and a shorted more rounded head shape. They have been issued with the identification code number CW036.

Ian

Corydoras arcuatus female

Picture courtesy Ian Fuller & Corydoras world

Thanks guys

Ian , I wondered that after reading about them in your book , I noticed the longer snout also .

They are 2 3/4 - 3 1/4 inches , should I expect them to grow any larger ?

C. arcuatus is a species that grow to a little over 2 inches, the CW036 ("Super arcuatus") grows to 3" plus.

At the time I wrote the breeding book it was not known that there were two distinct forms and because I did not have a picture of the original breeding male I used the image of what turned out to be a male CW036. This will be corrected in the second edition of the book.

Ian