DIFFERENT POPULATIONS OF CORYORAS DUPLICAREUS?

[cartouche]

Hi, I have an interesting problem. Four years ago I bought a group of CORYDORAS DUPLICAREUS and gradually I created a big breeding group of 30 fish. In contrast with some internet reports, the eggs of these fishes develop only within a very narrow range of chemistry, between pH 7,5+4 dGH - pH 7+5,5 dGH - pH 6,5+7 dGH.

Recently I bought another breeding group of (imported) CORYDORAS DUPLICAREUS that was better coloured, with the red spot shining like a neon even in darkness, and four days ago I had first 46 eggs from them. Considering that there exist conflicting reports on the ideal chemistry for Duplicareus eggs, I was aware that these fish may come from a different locality and may have different demands. Hence I held this group separated from my old Duplicareus and I divided their first bunch of eggs into 5 groups, each with different chemistry ranging from pH 6,5+2,5 dGH to pH 6,5+7 dGH.

My assumption was confirmed, although somewhat unexpectedly - the eggs namely hatched at all kinds of chemistry, although in some groups there were bigger loses than in others (in the morning the eggs were white and fungused, but it may be due to fungus quckly spreading from dead eggs overnight; next time I must confirm it). The most important finding was that these fish had very different demands from my old breeding group - which explains the discrepancy between my experience and some surprising internet reports.

It is clear that if Duplicareus is really only one species (and not more species with similar coulouring, as it often occurs in Corydoras), then there must exist several different populations in geographically isolated regions that are specialized in different water chemistry.

[NEONCORY]

Hey cartouche,

That is so interesting. Especially I, too recently obtained some C.Duplicareus although they were marked as C.Adolfoi at the local store.
They are not quite adult yet but another few months, they should be ready to produce some eggs for me. Although they have clean bright colors, they have orange than red you described.

Anyway, so I am SO interest to see what you find about them.

So I'll be keeping eyes on this thread. Catch you later.

[apistomaster]

Your conclusions may be correct or not.
It is also entirely possible that you are also just getting better at working with C. duplicareous.
It just seems like you need more experiments if you are trying to prove something. It is more of a hypothesis than a fact so far.

I have some experience with breeding C. duplicareous and I don't consider them to be the easiest Corydoras to breed because I have had some difficulty when it comes to getting good hatches. So I do share your interest in trying to figure out why this is the case.

[cartouche]

Your conclusions may be correct or not.
It is also entirely possible that you are also just getting better at working with C. duplicareous.
It just seems like you need more experiments if you are trying to prove something. It is more of a hypothesis than a fact so far.

I have some experience with breeding C. duplicareous and I don't consider them to be the easiest Corydoras to breed because I have had some difficulty when it comes to getting good hatches. So I do share your interest in trying to figure out why this is the case.

There's not much to discuss. The eggs of my old breeding group simply develop only within a very limited range of chemistry (I prefer pH 6,5, 7 dGH), while eggs of these new duplicareus hatch at pH 6,5, 2,5-7 dGH - and maybe even in harder water. You must be very careful, if you prepare hatching water for the old breeding group, because a deviation of mere 1 dGH from the ideal parameters causes significant loses or spin deformations. A bigger deviation kills 100% eggs. But these new duplicareus seem to have no special demands. These are simply two different groups of fish.

I always wondered why internet sources often don't list any special water chemistry for the development of duplicareus' eggs, and if they list it, they recommend very soft and acidic water. Many times I tried very soft and acidic water in the old breeding group, but all eggs died after 4 days. It seems that there exist no other appropriate chemistry than those pH 7,5+4 dGH or pH 6,5+7 dGH.