orydoras rabauti is a beautiful little catfish
that is often the subject of mistaken identity. Many pictures
on the internet are of another species (usually C.
zygatus) and shops routinely mix the two up. It’s
understandable; they really are very alike although it’s
rather easier to separate them in real life.
C. rabauti is a chunky fish with a rusty coloured
body and fins. It has a matt green stripe running the
length of its upper surface ending in a downward kink
at the caudal peduncle. Fish in good condition are almost
C. zygatus is slightly larger and more elongate.
It has a pinkish-gray background colour and the green
stripe has a slight metallic sheen and lacks the downward
kink. Most individuals have little copper “eyebrows”
which can be seen even in albino specimens. Adult C.
zygatus seem a little scruffy to my eyes, not something
that can ever be said about C. rabauti.
For breeding I used a group of large adult fish that I
had been conditioning on live worms and daphnia for some
time. These fish had spawned a couple of years before
when about two hundred infertile eggs were laid just below
the water surface and in an area of the tank that had
a lot of water movement.
laid just below surface
My group started to spawn again
in the summer of 2009, usually the day after a water change,
but once again the eggs were not viable. I had four females
and a single male. This is not an ideal sex ratio (more
males than females are recommended for corydoras breeding)
and may well be the reason for such poor fertility. Eventually
however from a spawn of around 200 I managed to collect
around 50 eggs that showed promise.
Tank parameters at this time were as follows:
36” x 12” x 12”
Air-powered sponge filter plus Fluval 3 power filter for
Pieces of wood with attached Java fern, floating plants
Other tank mates:
Small group of Brochis splendens
A video of a female depositing an egg on a floating plant
can be viewed here:
As before, eggs were laid in areas
of extreme water movement. Often right on the filter outlet
pipe or in the turbulent water where the current met the
front glass. Another favoured area was on the air tubing
entering the sponge filter. Some eggs were even placed
above the water line in the splash zone caused by the
I hatched out the eggs in a margarine
tub with a little methylene blue and a vigorous air stone
to prevent fungus. They took a little longer to hatch
than I expected and some fry had still to emerge after
a full week. When they did finally hatch they had already
absorbed most of their yolk sack and a few had deformities
of their spine. Some aquarists avoid the use of methylene
blue and one of the reasons given is that it can harden
the egg shells and prevent fry from breaking through and
hatching. I don’t know if this is the case here
as I’ve used it many times with no ill-effects but
this was certainly unusual
Although the adults of C. rabauti and C.
zygatus are similar, the fry could not be more different.
C. zygatus fry are cryptically coloured with
a typical corydoras fry pattern of mottled brown spots
and blotches. C. rabauti fry however have a fry
pattern that has both surprised and delighted aquarists
for many years and was the main reason why I wished to
breed this species.
The newly hatched fry showed hints of what was to come.
A dark band neatly encircled the fry to the rear of their
belly. Forward of this the head was beige with a neat
diagonal eye stripe. To the rear of the band the body
Newly hatched fry
1 week old
The fry were fed the usual fare
of micro worm and minute quantities of ZM100 fry food.
Each day I changed half of the water with aged water of
the same temperature. An apple snail was kept with the
fry. This eats any uneaten food and prevents a build up
of fungus on the plastic bottom which otherwise might
damage or even kill the developing fry.
After a week the young fish were starting to gain more
colour. The middle band had widened and spilled onto the
dorsal fin. The head was now golden-brown, still with
an obvious diagonal eye-stripe. The rear of the fish was
still largely transparent.
I split the group and moved them into two tanks with other
small corydoras and shrimp. One tank was on the top shelf
(warm) and the other was on the cooler bottom shelf. I
went on holiday for a week and when I returned the fry
in the warmer tank had not survived. Those in the cooler
tank were fine and thriving. I now had a couple of dozen
Two weeks old
- group of fry
I started to feed newly hatched brine shrimp and pre-soaked
crushed flake. Tetra Tabimin also proved to be a firm
favourite as it is with all Corydoras. The dorsal fin
was now chocolate brown and the middle band had widened.
The rear of the fish had started to turn a bluish-white.
The barbels and fins were now almost fully developed with
only slight webbing remaining between the caudal, adipose
and dorsal fins.
After about a month I noticed a
small number of fry had missing fins. I wasn’t able
to determine the cause of this but I offer up some possibilities.
• Genetic abnormality – possible but unlikely.
The adults were perfect specimens.
• Damage during the prolonged hatching – likely
• Fins nipped by shrimp during early life –
I haven’t heard of this but I suppose it’s
• Damaged by fungus or other disease – possible.
Four weeks old
Four weeks old
– fins missing
The pattern was now fully developed
and can be seen in the accompanying photographs. Three
distinct coloured bands from front to back – rusty
brown, black and bluish white topped off with a chocolate
dorsal fin. The eye stripe had faded by this time but
was still just about visible. The chocolate coloured pelvic
fins completed what was altogether a stunning little gem
of a fish.
weeks old – portly little fellows
Two months old
– still a handsome fish
From 6 weeks or so the fry pattern
gradually faded and the familiar adult colours took their
place. These little fish grow rapidly and by three months
old were a sellable size.
Corydoras rabauti make a splendid breeding project
for the intermediate or advanced fish breeder. Some patience
and persistence is required to get the adults to spawn
but the sight of a tank full of fry is payment in spades.
The adults themselves are perfect community fish.
All Image's by Author