Re: Dicrossus Filamentosus

["David A. Youngker" <nestor10@mindspring.com>]

When I first started to keep D. filamentosus, I was also in a situation
where I could glean them as "contaminants" from Cardinal shipments, of all
things. That was back when they weren't considered a "commercially viable"
fish because of the difficulty in keeping them healthy. The hobby had some
ideas about water quality then that we know to avoid now, though.

Because of the types of fish they were mixed in with, I originally thought
to keep them as I had Heckel Discus - very warm, very pure water. At the
time, I thought 86F was a tad on the "low" side of their range, but I've
since concluded that 84-86F range seems to keep them the healhiest over the
long term. They are as sensitive as Altums to temperature fluctuations, and
stability is more important than precision with these fish.

Normally, maintaining a fish in hardness parameters outside of its natural
range seems easier in keeping soft water fish in harder waters than the
other way around. D. filamentosus seems to be the exception to the rule - as
hardness increases their lifespan and "quality of life" diminishes. And
breeding and grow- out are definitely troublesome in all but the purest and
acidic of waters. Most of the problems with fertility seem to stem from the
water parameters rather than the couple's compatability.

This fish also has a definite love affair with plants. (Try that in a tank
that's halfway to the boiling point!) Tom's report of his spawning on a
plastic Ludwigia leaf is not really uncommon. It's been my experience that
they prefer a broad horizontal leaf to just about any substrate location.
The few I've had that bred near the substrate did it just above the
groundline on some root stock.

I think that much of the female's "indifference" can be attributed more to
the tank environment than to particular habits or traits. I get the
impression from watching them that guarding the nest and brood is dependent
on two distinct strategies. The male's role is to keep any threats from
entering an established perimeter, and his defense is a more active,
thrusting type. In this way, a normally shy and unobtrusive character like
the filamentosus can put his body type to best use - a quick, surprising
dart ending in a body nudge or small nip, then a quick retreat back to cover
to assess its effects. It's quick enough to surprise and irritate even a
larger fish, appearing to increase its anxiety to a "fight or flight" mode.

If it's flight, then that's obviously OK with Papa. If it's a fight, and the
outcome uncertain or disadvantageous to the dicrossus, then it can
immediately dart for cover and try to distract the fish away from the area.

Should the threat gain entry within the perimeter, it becomes too close to
"home" to continue the fight unless _both_ fish can effectively deter the
assault. Any unnecessary scuffling around the nest might expose an otherwise
hidden or unknown asset. And there's always the chance that said threat came
in from an angle which didn't catch the attention of the vigilant male. So
the female seems to spend most of her time in more of a "baiting" mode, and
sometimes appears to tend the flock only when absolutely necessary. In the
meantime, she depends _very_ heavily on a vegetative environment to not only
feed the brood, but hide and protect it as well.

I don't believe that you have to go as low as the 3s for pH, though.
Anything below 5 certainly works, almost to being advantageous. And for the
greatest success, either in hatch- out or early grow- out, you can't hardly
get around using anything but the purest of water. I use straight peat-
filtered RO (now) or rainwater (then), but avoid DI for this purpose only.
Why? Because RO _does_ leave a slightly higher percentage of "brine" than
does DI, which can approach too closely to distilled. For some reason, RO
seems to work better than the purer DI when adding the peat, even though I
believe the peat's limited ion exchange is more than sufficient to handle
the minute traces of "hardness" left. Perhaps because the peat needs
_something_ to exchange ions _with_, and the elements it's adding are what's
really beneficial?

Most of the clutch's fungus problems can also be pinned down to the water's
hardness. Outside of the expected natural ranges in water parameters, it's
the male's sperm, and to a lesser extent the female's egg, that's doing the
actual suffering. These little single- celled personalities don't "cotton"
too well to higher osmotic pressures than those for which they're
"designed".

When the fry reach the free- swimming stage, they stay very close to the
substrate and vegetative surfaces, nooks and crannies. As they grow, you can
actually see them "nibbling" at the surfaces, much as do Krib fry. This is
where a heavily- planted, slightly mulmy tank can actually work to your
advantage, as there will be a wealth of infusoria for the fry to graze on.
And they look for food here because of the type of environment they're
normally born into - rain wash, in essence, with little, if any, waterborne
life due to its innate sterility. Not only does the acidity prohibit "free"
growth, but a lot of the humics in the water act as bacteriostatic agents,
too.

Strained Artemia nauplii, as has been suggested, can sometimes be slightly
problematic because of their size. The suggestion of microworms is good, as
they're easier for the fry to gobble. Another good choice are Rotifers.
Infusoria are always welcome - and here, a good- sized ball of Java Moss can
be extremely helpful. Even finely- crushed flake (to almost a powder),
soaked so that it will stay down when introduced, will often be accepted
(seems almost "mood" dependent, though). After about 3-4 days would be the
best time to start introducing the nauplii, and after a couple of weeks you
can start in on some of the smaller Daphnia. Usually by the third week they
can handle just about anything you care to throw their way.

And they do grow slowly, as do fish like Cardinals. Any fish born and reared
in waters so pure can't really afford to develop a metabolism that's too
accelerated, and this "evolved" trait isn't likely to change just because
more minerals are present. Or present in the wrong proportions...

-Y-

David A. Youngker
nestor10@mindspring.com




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