They, like many tetras, are egg scatterers and boy can
they scatter eggs! Your question about methodology is
certain appropriate, because there are also Characins
which, in at least one case, hang eggs on leaves above
the water. Several members of another family of
Characins (there are a bunch of Characin families)
seem to practice a sort of internal fertilization, the
females laying their eggs some time after coupling.
One can read of Piranhas spawning over nests.
The Mexican tetras are found in so many places that
one gathers that such adaptable fish should be easy to
feed most anything. Sounds like yours are doing well.
I would guess that your water isn't going to be harder
than what they were in and so that should not be an
issue.
Before you move them, maybe give them a fair-well
partial water change and meaty feeding. The tetras
I've seen spawn have generally all joined in the
frolic. I don't know if all of yours would or if some
would feast on the products of others. In any case you
should have enough eggs and fry.
Can you raise or lower their temperature to the upper
60sF/20C ? Don't know if that is necessary.
The eggs remaining after you remove the adults should
hatch in the second day and they should be free
swimming by the 4th. They can take newly hatched brine
shrimp and commercially produced fry foods. (Or in a
oinch, you can wrap some flakes up in a handkerchief
and pound them.) The article alluded to below suggests
that if they are too crowded, that the larger
individuals will work that out, perhaps giving you a
perponderance of females.
Aquarists keeping tropical fish too often make the
mistake of keeping them with smaller and eventually
edible tankmates. They also may confine them to
insufficiently large aquaria. (You aren't.) That gives
those tetras a bad rap for doing what most any fish
will do.
I have a hunch that many of the more conscientious
aquarists have established conditions where tetras
have spawned, often on a regular basis, in their
aquaria and have never realized it. I discovered a
couple of species would be triggered into a spawning
melee when the Saturday sun would clear the neighbor's
roof to the east and shine into the 40-gallon tank.
They gathers around a large, fine-leaved water sprite
and really made whoopee. (A large school of armoured
catfish accomodated the little whoopees.) From limited
experience with other tropical egg scatterers and
hangers, a number of them are also stimulated to spawn
by the first rays of the sun.
Are there some Cyprinids from American habitats that
are also prompted to procreate by the first strong
light of the morning?
A fun and useful article on them is found at
http://www.aquarticles.com/articles/breeding/McFarlane_Astyanax.html
Good luck with them, though you seem to be doing a
fine job of making your own luck. All the best!
Scott
Thorncreek drainage, Illinois
--- geoffrey kimber <gkimber2 at gmail.com> wrote:
> Does anyone have any information about breeding
> mexican tetras?
>
> I currently have about a dozen in a 29 gallon tank,
> but I will be
> moving them into a 55 pretty soon. I caught the
> fish in a high flow
> region of a beautiful rocky river (the nueces) about
> 2 hours west of
> San Antonio.
>
> the males have colored up nicely and the females are
> getting bulky.
> I'm wondering if the fish just scatter eggs or if
> they use another
> fish's nest. I'd also be interested in knowing how
> long the eggs take
> to hatch and if baby brine shrimp would be a
> reasonable first food for
> the fry.
>
> Geoff Kimber
> fredericksburg,va
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