have already reported about the
spawning of my Walking Catfish pair in Datz 7/2004 ("Successful
spawning of the Walking Catfish in the aquarium”,
p. 12-15). and at that time
the animals without my assistance spawned four times in
a period of only five months. Then their reproduction
interest disappeared very sudden for some time and didn’t
want to wake up again even after several months.
What had happened? Was the spawning
season for the animals, at least in my aquarium, at an
end? Were there otherwise any differences (on-due dates)?.
The couple were still in top form: Male, like the female,
were avaricious eaters and otherwise did not show any
deviations in their behaviour and the pair-bonding was
unchanged. The initial situation for another spawning
seemed to be therefore favourable for me but obviously
there was a lack of certain circumstances to push forward
again the courting formality so often to be watched and
to initiate (activate) a further reproduction.
Patience pays off:
Certainly I still had in
memory the breeding-reports primarily belonging to the
species of the genus Corydoras in which it is
recommended one may imitate the rainy season largely since
the spawning season of the animals falls in this phase.
Therefore at first I started to exchange a third of the
tank contents for such cool water that the previous water
temperature of about 25 dropped to 22° degrees Celsius,
however the result was rather disappointing. Although
the Walking Catfishes more often again started to swim
behind each other, however I could not observe the typical
courting before spawning much less the real reproduction.
At least the cool fresh water supply alone therefore could
not be the decisive factor.
Male piebold Walking Catfish
Female albino Walking Catfish
An alternative discussed in an Internet
catfish forum, namely the sole reduction in the water-level
about ten centimetres under retention of the usual temperature
of 24° degrees Celsius, also did not lead to any success.
Further attempts of which I brought respectively additional
factors in the game and varied them, finally provided
the desired result - my Walking Catfish pair spawned once
more!. In the morning at eight o'clock the female after
many hours of courting they ejected eggs. A number of
further matings, which dragged on up to the early afternoon,
followed after more than about six hours. At first and
to the end of the spawning act, only about 100 eggs were
given. Within the hours between this however, it was also
500 and more.
this mating, about 500 eggs are ejected.
With on an average given to about
200 eggs per mating and at least four matings in a hour
this 40 centimetres long female almost dropped 5.000 eggs.
This is remarkable in this respect, as the female has
grown in the last nine months, a further two centimetres,
however the number of eggs at that time had been considerably
under 1.000. The animal ( female Clarias batrachus)
however has strongly grown in the breadth at this time
especially the first half of the head and belly. In its
length it has been growing since the last 18 months, only
about two centimetres, and obviously seems to be more
massive than before. This indicates that eggs must have
developed constantly in the belly of the female (now 5.000
eggs, before only 1.000!). These eggs, however, would
have not been ejected not until later without the stated
changes. But I will come back to that later.
In the meantime after another three, in the interval of
approximately a month, successful tests of sticking to
the same "recipe“ I have arrived at the conclusion
that the reproduction, specifically of Walking Catfish's,
can be initiated in relatively short intervals of a few
weeks if the following framework conditions are created
or changed gradually. They simulate at large the natural
environmental changes as the results show, especially
during the monsoons with their long continuing strong
rains and following inundations in the native countries
of these animals.
All factors together lead to spawnings in inundated areas
like paddy fields, in which the water is already, due
to the low level, warms up quickly to 28 or even 30°c.
There the older animals which have lived before in the
most different water conditions, a food area opens itself
up which is rich in insect larvae, worms and so on and
also where their descendants in this regard were looked
after very well and additionally the young catfishes there
can find possibilities of shelter.
The experiences introduced here can presumably be also
used for other Clarias species, if not even transferring
it to some other catfish families or motivating to think
a little in this direction.
At first the tank size must be correct of course: If one
wants to take a Walking Catfish pair to spawn, then the
aquarium should hold at least 500 litres!, then it must
be sexually mature animals. Even if my Clarias batrachus
pair spawned for the first time with a length of almost
30 centimetres, the beginning of sexual maturity might
lie considerably under this mark, at about 20 centimetres.
Either one is safe to have a pair already in this size
or one has to found for itself such a pair from a group
of either four or five animals, going beyond what is required,
or sufficient with the fish already there!
If one is not able to distinguish the sexes due to their
appearance - the female is more corpulent and more massive
than the male. Also outside the spawning season –
one can observe the differences with a length of about
20 centimetres due to the form of their genital papilla.
The male is sharpened at the end, with the female however
short and oval.
genital papilla of the male Walking Catfish
papilla of the female Walking Catfish
A couple well harmonizing with
each other is really looking for the proximity to each
other. The animals conspicuously frequently go "on
physical contact". They rest approximately in such
a way that they make and keep in touch with each others
fins or barbels.
At first the animals are kept for about three
months at a water temperature of at most 23° C. This
temperature might move for most tankmates rather at the
lower limit but still should still be unproblematic. Stopping
a high water temperature for a relatively long time will
make the sensibility of the catfishes correspondingly
increase to react quickly with a first reproduction at
a later warming and a change of other substantial factors.
At this time one should refrain from the serving of living
food and confine oneself alone on cichlid sticks, tablets,
Forelli (Trout feed) and similar. The animals also should
get food only once a day and then only so much food so
that they are always still hungry. The usual water changes
of about 25 per cent have to be carried out like always
at regular intervals.
Following these twelve weeks the animals are fed particularly
well and alternately with their favourite living food
like Tubifex or earthworms. If one can only go back to
frozen food even with bigger specimens, red mosquito larvae
suites quite well. In any case you should feed daily now,
By the way, what the animals eat best depends which food
was given to them in their youth. Clarias batrachus
keepers have confirmed that animals raised in aquaria
to which exclusively several ready convenience food mixtures
had been given exclusively in the first months of life
soon ate those avariciously. This food, whether food tablets,
Acipenser pellets or cichlid sticks, are able to "recognize"
the food even after a long time. In such a way raised
Walking Catfish then used to their preferred convenience
food clearly over even living food, which they have not
got until later and which is offered as a trial.
Male Clarias batrachus eating an earthworm
Both partners eating "Forelli”
Parallel to the food rearrangement
a generous water change is carried out by approximately
half of the volume within the next days. The supplied
cooler water can even lead to another, merely short-term
reduction in the temperature of about one to two degrees.
Feigning an inundated area of the tank contents by supplying
a good water preparation by filling up again by about
85 per cent of the total volume and lowered again by about
ten per cent on the day after the water change so that
the water level is only 45 centimetres in the end at a
height of 60 centimetres. Anyway if the aquarium is only
50 centimetres high, then a lowering at five centimetres
each in of these two steps to about 40 centimetres is
recommended. The leaving out of the top of the filter
can lie over the surface so that the water can audibly
flow well into the tank from above. To increase the flow
effect in this place further, a more efficient internal
filter should still be placed if necessary.
"Barbels to barbels”: If you have a good
harmonising Walking Catfish pair, both partners
will show the feeling of togetherness like here.
In the end the temperature is increased
to 28° degrees Celsius gradually within the next three
days after the variations in the cooling which the rains
bring about in nature been lowered to the described 21
to 22° degrees Celsius. Since due to this warming
and the more active way of life, the appetite of the animals
still grow. They are then further fed extensively with
their favourite foods.
Clarias batrachus pair in a tank with lowered
water level and increased temperature, the female
seems to develop more and more eggs from day to
First spawning preparations:
Due to the giving
of rich living food, especially due to the induceing of
fresh water, the lowering of the water level and then
the increased temperature, the female soon visibly gets
spawn and with the light preferably turned off the animals
start courting. An important prerequisite for it might
represent the changed water supply and also: The water
pouring from above like rolling oxygen pearls causeing
noises that are made also at the time of the monsoon rains.
The perception of these noises should also have a signal
effect for the animals.
Courting of my Walking Catfish
pair in the evening (with light turned off)
Many a reader may smile now but
this effect can still be strengthened by a background
noise like loud music for one to two hours on the day.
These sounds in connection with the stronger flow are
apparently an indication for the catfishes that the rainy
season with their monsoon thunderstorms, or that the rising
of the waters is coming, or has already started.
Both partners start with the first dig activities which
are clearly different from those of the animals when they
rummage the bottom for food. They are concentrated on
a certain place, namely the latest spawning place and
are accompanied mostly by the wafting movements of the
chest and tail fins which becomes particularly clear when
digging of the pit by the male.
Digging for food however, except
naturally for the place below the usual feeding place,
is carried out over the complete tank more or less without
any aim, by head and then the third of the body being
drilled to the sand or gravel ground.
If the pit is dug, the first mating's
follow at which however no eggs are delivered. From time
to time the animals take breaks of several hours over
a few days which are however interrupted by intense courting
and recent mating's again and again. These "feignedly
mating's" might accelerate the formation of further
The first matings without ejecting eggs
Then it is ready!
As soon as eggs in a sufficient number have developed
and the female shows herself once more to be ready for
mating, the spawn finally is ejected after further embracement.
To avoid a fungal of all eggs adhering to the bottom gravel,
especially at the high water temperature, it is advisable
to add a product against spawn-fungal. In addition is
to adjust the heater one to two degree lower.
First matings with only a few ejected eggs
Nevertheless at such precautions
a larger portion of eggs becomes fungal, particularly
after about 15 hours. Due to the variety of the fungal
eggs - from the calculated 5.000, 10% would hatch, and
therefore over 4.500 threatened to ruin the water - the
water starts to become cloudy which can only be stopped
with a very good filtration. I warn against a water change
in this phase. Due to the disturbances connected with
that it can said be that the male does not return to the
spawning place any more and stops the care of the offspring,
the clutch is then ruthlessly exposed to possible spawn
predators. Already a couple of Botia lohachata
or Chromobotia macracanthus are able to track
down unerringly the few young fish hatched out and to
Some of the large number of
eggs at the bottom of the shallow pit
The very high contingent of fungal
eggs could be explained with my animals in that the spotted
male originated from a hybridization and has only a restricted
fertility rate. The number of the eggs from which young
fish can develop also after fertilization would then already
be very low, however this is an assumption. Under circumstances
the change of other water parameters or use of another
product against spawn-fungal could bring better results,
however to do this it requires additional tests.
Here the first eggs already have fungussed after
However it already now seems to be sure that the eggs
of Clarias batrachus are generally more delicate
against fungal infection. A British aquarist reported
to me of a coincidental spawning of his semi albino Walking
Catfish couple. There a large portion of the eggs also
fungussed after 20 hours and only a few larvae hatched
out. With an experimental attempt carried out in Indonesia
in 1990 to transport the eggs of Walking Catfishes (here
it can only have been the wild form) into aquaria and
to let them develop in those tanks, separated from the
parent animals, they indicated explicity the fungal infection
of the jelly-like mass which surrounds the eggs. In an
abstract given at FishBase/LarvalBase it is recommended
to water the eggs immediately after the spawn act for
five minutes in a one per cent sodium sulphite solution,
to wash them three times into tap water and not until
then to give them back to a separate tank, so a fungal
can be avoided. However, this procedure may be left to
these persons who actually want to raise young animals
in a larger number and who are already clear in their
minds where to distribute them later.
Obviously the female is able to eject the number of the
eggs altogether on one spawning day. Only so it is to
explain that the very same animal can deliver only a few
hundred to at most 1.000 eggs, and only four weeks later
however, a couple of thousand eggs. Presumably not only
the intervals play a role here between the spawning procedures
after which a longer period leads to a higher number as
described in this case with 5,000 eggs at the beginning,
because even if such a high number of eggs the female
can theoretically eject in the course of a day, because
it is already available, it is not automatic that she
must deliver them all. In fact further circumstances like
water-levels or temperature and the other fish kept together
with the Walking Catfish should be of importance. If the
water values are not optimal for the female, and if it
feels disturbed from other tankmates or looks at other
fish as possible spawn predators, it delivers only a lower
number of eggs, possibly merely the minimum number of
eggs, whereas at good conditions it is ejecting all eggs
at the matings on a day.
If pairs do not come into reproduction
despite starting the described changes it is highly recommended
furthermore for the best feeding and the perpetuation
of the temperature chosen at 28° C and to last for
four to five days with additional water changes (a third)
at which the level alternating is to raise and to lower
by about 15 per cent.
Water level raised again,
then it was again lowered, after two more changes
the pair spawned
As recently as with the slipping of the fry the female
returns a few times to the edge of the nest. It comes
to rapid movements of both animals there. The male tries
to push the female away immediately by "rebelling"
vertically in front of his partner, taking a threatening
attitude with an open mouth and beating with the tail
fin against the body of the female. However since the
aggressiveness of the female animal suddenly increases
at the same time once again, it can be that, especially
when pursuing other fish, it penetrates unintentionally
into the immediate nest area whose guarding of is incumbent
alone for the male. The male will then fend it off with
hectic, extremely fast swimming movements. These are,
however, so stormily carried out with such a speed that,
especially big animals, thereby (rub the wrong way up
to filters, stones and so on, without biting each other)
are able to suffer injuries of the fins and barbels.
Aggressiveness of the female
and male animal suddenly increases at the same time
However the keeper does not have
to worry because of this yet because Clarias batrachus
are quite robust and seldom affected by illnesses,
like almost all catfishes. Injuries of the fins have already
healed completely after a few weeks. Even damaged and
almost whole snapped off barbels have regenerated itself
again at this time. The fish are however more delicate
of injuries on the skin. These can infect quickly, and
cure themselves comparatively slowly, even at the best
water care and the use of a special mucous membrane protecting
water preparing product.
Walking Catfish with three damaged barbels which
already have begun to regenerate
If the couple has stopped the care
of the brood after some days, the temperature can be lowered
to about 24° degrees Celsius again gradually. After
a break of some weeks one can keep this value as a temperature
before a recent change of the factors stimulates a further
Already sexually mature but even younger animals can more
frequently reproduce in comparison with fully-grown specimens
and undercut even the four week distance, though altogether
the number of eggs per spawn act with older females is
higher about a multiple. Since mine are only two years
old and with its 40 centimetres, not quite fully-grown,
in the end attainable numbers from 8.000 to 10.000 eggs
should be realistic.
How is it with the maximum size of the animals in the
aquarium at all?. At least the albino and partial albino
specimens who are offered now and then in the ornamental
fish trade usually don’t get much bigger than 40
centimetres in size and according to feedbacks of Walking
Catfish keepers even after many years, do not exceed the
mark of 45 centimetres (in one case however there is a
reported specimen of 52 centimetres). Therefore different
from the predatory catfishes of South America who nearly
almost get bigger, one can keep this species in the long
run in a one and a half and up to a two metres long tank.
Full grown Clarias batrachus pair, both
partners are mostly together
Probably also with
Walking Catfishes which are spawned in warmer climates
for the food extraction in ponds, a simultaneous spawning
of all sexually mature females probably is reclusively
possible by the natural methods described here. An artificially
initiating of the mating in the conventional means of
intra-muscular injection of hormones with the female is
not inevitably required with Clarias batrachus
if one wants to spawn these catfish at a particular time.
Surely it is not advisable to persuade the animals continually
spawning by a permanent change of the factors influencing
their reproduction. Spawn acts too often provoked in this
way might in the long run even weaken them. The use appropriately
makes sense if even adult pairs have not reproduced yet
at the otherwise optimal keeping conditions.
Note: This article was first published in April 2006 in
the German publication: "Die
Aquarien und Terrarienzeitschrift" (Datz) 59 (4):
My thanks apply here for the Datz
editorship and their editor-in-chief, Rainer Stawikowski,
who gave me kind permission to publish the article on
ScotCat. Here is the original text, only
some photos have been updated and new ones added.
(C) Copyright text and photos: Datz