Starting with Corydoras

Author: Ian Fuller

Over the years I have been asked many questions about keeping and
breeding Corydoras Catfish, by people that would like to start
keeping them and others that have them but would like to try
and breed them. The ten most popular questions I have listed
below. The answers I have given to these questions are based
on the many years of experience I have gained with keeping and
breeding these wonderful little fishes, and are meant as a guide
rather than the rule.

Questions

1. How big do they get?
   
2. How should I set up a tank for them?
   
3. How many can I put in my tank?
   
4. What species are best to start with and how expensive are they?
   
5. Where are the best places to get them from?
   
6. What should I look for when buying?
   
7. What do they eat?
   
8. How can I sex them?
   
9. Can I breed them?
   
10. How many species are there?

Answers

1. Corydoras pygmaeus and Corydoras hastatus are the smallest described
   species, at twenty-five millimetres, with Corydoras barbatus
   possibly the largest at one hundred millimetres. (2PICS)



2. There are many ways of setting up tanks that are suitable
   for Corydoras, I think the main criteria would be what are the
   ingredients needed to create the ideal Corydoras environment?
   For me these would be, a) Tanks that are large enough to house
   the fish you intend to keep. (See answer 3). b) A smooth substrate
   to prevent damage to mouth parts. c) Quality water = Clean and
   aged for at least three days, with near neutral values pH6.8
   - 7.4, GH10 - 15, and a temperature of between 70 - 76 degrees
   Fahrenheit would be a good starting place. Most water authorities
   supplies although they may vary in values from one authority
   to another, are quite adequate for most species.
   
   There are two types of set up that I use. The first is a community
   tank set up that is primarily aimed at housing Corydoras, in
   which other fish are added to give the tank a visual balance.
   External power filters are used on my community tanks because
   of the substrate I use, which is either fine smooth gravel no
   larger than one and a half millimetres, or well washed river
   sand both of these would very quickly clog under gravel filters.
   The depth of the substrate is quite shallow no more than fifteen
   or sixteen millimetres deep, this allows the Corydoras to search
   out food particles right down to the base of the tank. This
   prevents the problem of food particles filtering deeper than
   the catfish can reach and souring the substrate. For tank decoration
   I use pieces of bogwood with either Java Fern or Java Moss attached,
   and although the substrate is fairly shallow I have found most
   plants such as Cabomba and Elodia will and do grow well. Java
   Fern is particularly good because it can be attached to a variety
   of tank decorations, be it wood, slate or rocks. If it is held
   in place with the aid of an elastic band it will attach itself
   in a very short space of time.
   It is a very tough plant and will grow well under a wide range
   of conditions. The second type of set ups that I use are purely
   for breeding and raising fry. These tanks vary in size from
   20cm x 20cm x 20cm which house small species, to 90cm x 45cm
   x 20cm which are stock /fry rearing tanks. The size of the tank
   for breeding is relatively unimportant so long as it is large
   enough to house the fish that you are intending to breed. In
   the small 20 x 20 x 20cm tanks I keep and breed small species
   like C. xinguensis and C. griseus.
   
   All of my breeding and rearing tanks have a ten to fifteen millimetre
   layer of either river sand or fine smooth gravel in them. I
   have in the past and do still occasionally use tanks without
   any substrate at all in, these are mainly for quarantining or
   raising delicate fry in where uneaten food and waste matter
   can be seen and removed easily with the minimum of disturbance
   to fish or fry concerned. The types of filtration used in the
   small 20 x 20 x 20cm tanks are sponge filters. Box filters are
   used in the medium sized tanks (45 x 25 (30) x 25cm), and in
   the larger 90 x 45 x 20cm stock/fry rearing tanks the filters
   are home made under gravel box types with power heads fitted.If
   I need extra filtration I use an external canister type filter.
   
   
3. The number of Corydoras that can be housed in any one tank is
   much a matter of choice, but if you bear in mind that they are
   shoaling fish and are generally happiest in-groups of six or
   more. My recommendation would be six to eight inches of fish
   to every square foot of base area. When calculating do not count
   the caudal fin (tail) as part of the fishes length, its the
   body length that counts.



4. In the main most of the Corydoras species that are
   available are quite hardy and not too difficult to keep and
   maintain in good health. Therefore the choice of species to
   start with will probably have more to do with finance than anything
   else. There are species such as C. aeneus and C. paleatus that
   have been in the hobby for many decades, these are being commercially
   bred in there thousands in far eastern fish farms and can be
   bought for one or two pounds each depending on their size. At
   the other end of the scale there are species like C. solox and
   C. pulcher that have asking prices of thirty pounds or more
   each. For those of you that have never kept Corydoras I would
   recommend some of the less expensive species, which should be
   available for under a fiver each, some of them are quite striking
   in their markings and are ideal species to start with. Here
   are a few to look out for. C. trilineatus and C. schwartzi have
   sharp black and white markings. C. metae, C. meleni, and C.
   rabauti have tan coloured bodies with dark bands across the
   back. Then there's one of my all time favourites C. arcuatus
   (the skunk catfish), with its white body and arching black band
   that runs from snout to tail. For those of you looking to try
   your hand at breeding need look no further than Corydoras aeneus
   its albino form or C. paleatus, these are probably the easiest
   of all Corydoras to breed.



5. There are several sources to acquire Corydoras from
   some of them are better than others. The first place to look
   is in your local aquatic shop the choice of species there may
   be limited, but most if not all aquatic shops will have at least
   a couple of species on offer. To find a larger choice of species
   you may have to travel a little further a field to one of the
   shops that specialises in catfish. There are a few of these
   establishments around the country where the choice of species
   will seam almost endless. I have been known to make a round
   trip of over four hundred miles in a day because certain shops
   have got the species that I have been searching for. A third
   source of supply is from someone that is breeding Corydoras.
   The biggest advantage with buying from a breeder is that you
   will know the conditions the fish have been bred and raised
   under, how old they are and the best types of food to feed them
   on. This last point is something that is almost impossible to
   determine with wild imported fish.



6. When buying Corydoras there are a number of important
   things to look out for, to insure that you are selecting good
   quality stock. It is probably easier to list the fish to avoid
   and add the good points later. a) Sunken eyes, b) Red blotches
   in the abdomen, c) hollow belly, d) inflamed gills, e) Missing
   or badly worn barbels, f) Deformities.
   
   Fish that have sunken eyes are old and almost at the end of there
   lives. Those fish that are showing red blotches in the abdomen
   have an infection in the gut, which in most cases is fatal.
   These fish should be avoided and not given a second look because
   the chances are they will not survive for more than a few days.
   Fishes that have sunken or hollow bellies may survive given
   the right kind of conditions and feeding. I would still leave
   these fish alone.
   
   Reddened / inflamed gills are also a sign of infection which
   may or may not be easily cured, if the fish was rare and the
   price was right then I might take a chance, but normally I would
   leave these fish alone. The barbels of Corydoras are very important
   sensory organs used for detecting and searching out particles
   of food from the substrate, and were the females are concerned
   playing a major part in the breeding activity. Badly worn barbels
   may result in infection and mouth fungus so again these are
   fish that I would avoid. Any fish that are showing deformities
   are definitely given a miss, although they may be perfectly
   healthy they may pass on their deformities to their offspring.
   Freshly imported fish quite often arrive with damaged Finage,
   splits or with pieces missing out of them in most cases the
   damage will grow out and is not normally a danger to the fishes
   health. Now that we've seen the undesirable fishes "what does
   a good one look like" I hear you ask, well a quality Corydoras
   should have. A full rounded body, sparkling eyes, good barbels,
   a full set of seven fins, the flanks and gill covers should
   be covered by a metallic sheen and finally it should be reasonably
   active, although there are some species are far more active
   than others.



7. The choice of food is very important with any fish
   you keep and not just Corydoras. I use a variety of foods both
   commercially manufactured, as well as cultured and collected
   live foods. My feeding program is based around a staple diet
   of either a pre-soaked (so it sinks to the bottom straight away)
   quality flake or sinking tablet food. The tablets are crushed
   before given to the smaller species and crushedto a fine powder
   for fry. Live foods come in a variety of forms the following
   are the ones that I mainly use, none aquatic = Micro Worm, White
   Worm and earthworm finely chopped. Aquatic = Brine Shrimp, Daphnia,
   Tubifex and Bloodworm. All live foods are given in small amounts,
   that is to say as much as the fish will eat in five or ten minutes.
   There are also frozen foods that are very good especially during
   the winter months when live foods can be harder to come by,
   the range of frozen foods are quite extensive from Cyclops to
   muscles and these day's most aquatic shops stock them. It doesn't
   hurt to try these out now and again I've not found any that
   my fish won't eat, although some may need grating down to a
   size that can be consumed easily. During the summer when Daphnia
   is plentiful I will collect as much as I can, drain off the
   water when I get home and freeze it in plastic bags. I roll
   it out flat so that it is in sheets of about the same thickness
   as a medium slice of bread, (10mm thick) this makes it easier
   to break pieces off to feed to the fish, and each bag contains
   enough Daphnia to feed all my fish. Feeding takes place twice
   daily when ever possible. When time permits the morning feeds
   will consist of flake (pre-soaked) or tablet foods only. In
   the evening the tanks that are scheduled for water changes have
   this done first, then the fish are fed, however all the fry
   tanks have daily water changes before feeding commences.



8. Sexing Corydoras is not always the easiest thing to accomplish
   especially with freshly imported fishes, so I will explain how
   I go about the task. To start with there are three areas where
   I look for differences. The first is colour, which is probably
   the easiest area where differences will show. With most Corydoras
   species there are no discernible colour differences, but in
   those that do show colour dimorphism it's the males that poses
   the brighter more intense colour patterns. There is however
   a danger here because with some of these species the colour
   differences are so great you could quite easily think that you
   are looking at two separate species. The first thing to do is
   ask the retailer if they have been brought in as the same species,
   if they were then there's a fair chance that they are the same
   species. I would then take two of the brighter coloured specimens
   to every one of the lesser coloured ones. If there is any doubt
   then I would take equal numbers of each. Most Corydoras species
   belonging to the 'elegans' group do show colour dimorphism.
   
   The second area I look at is the Finage. Mature male Corydoras almost
   always have longer and more robust fin spines than females in
   particular the pectoral fins and to a lesser extent the dorsal
   fin, with some species the differences are so small that it
   is virtually impossible to see. With other species the differences
   are quite dramatic to the point were the males fins can be twice
   the length of the females.
   
   When there are no discernible differences visible in the Dorsal or
   Pectoral fins, the area I look at next is the Ventral fins.
   If there are any fin differences to be seen at all it will be
   here with males having longer, narrower and more pointed ventral
   fins than the females which will be far more rounded and fan
   shaped.
   
   The third and final area that I look at is the body, when viewed
   from above the widest part of the females body is at a point
   just forward of the insertion of the ventral fins. In males
   the widest part of the body is at or just behind the insertion
   of the pectoral fins. When viewed from the side females show
   a deeper more rounded body shape, were males should look slender
   and far more streamlined. There are other characteristics that
   can also help to differentiate the sexes, for instance C. barbatus
   males have bristles on the cheeks and females don't. So with
   species that are difficult I will look for anything that can
   separate them. On the occasions when I find it impossible to
   separate the sexes I will buy at least six specimens or more
   if the price is right. Once you have had the fish for a while
   and conditioned them the sexes will be relatively easy to separate.



9. Breeding Corydoras in its self is not difficult, the fish
   do that with relative ease all on their own, the difficult part
   is triggering them to do so in the first place. There are many
   conditions that need to be met before they will breed. Some
   times all that is required is a change of water of the same
   temperature to set them of (C. pygmaeus). The next stage would
   be a change of water that is slightly cooler, five or six degrees
   Fahrenheit is enough to promote spawning interest, C.aeneus,
   C. paleatus and C. panda are typical of the species that will
   respond to the cold water treatment. Once the basic water change
   methods have been tried then things start to get a little more
   difficult and other methods need to be used. The one thing that
   I do when trying to encourage a species to spawn is only try
   one thing at a time, this is because the first thing you changed
   may have been the right trigger. The second change may counteract
   the first and put the fish off spawning altogether. This may
   sound a bit like basic common sense to many of you, but it is
   surprising how many people tell me all the things that they
   have done to try and trigger there Corydoras to spawn. When
   asked they tell me several condition changes were made at the
   same time. I would also recommend keeping notes, as in my opinion
   they are invaluable especially when trying to breed some of
   the more difficult species. These notes can be referred to at
   any time to see the changes that have been made, or used to
   help formulate a series of changes that you think may trigger
   a spawning. The following is a list of the things that I would
   do in order to encourage a species to spawn given that the fish
   are in spawning condition. a) A weekly water change with no
   temperature change. b) Twice weekly water changes with no temperature
   change. c) Daily water changes with no temperature change. Then
   a, b, and c, again this time reducing the temperature by six
   to eight degrees Fahrenheit, after the cooler water changes
   the same sequence would be applied using warmer water again
   six too eight degrees Fahrenheit. There are some species of
   Corydoras that prefer warmer temperatures C. gossei is one of
   these. I will change the same amount of water approximately
   fifty percent for every water change made to maintain consistency.
   My next move would be to extend the time between water changes
   from one week to two weeks and then three or even longer, first
   with equal temperature water then with cooler water. If all
   these measures failed then I may try reducing or raising pH
   values, then the general hardness lowered or raised.The list
   of things that could trigger a spawning is endless as is the
   time needed to implement them, so I would say the main ingredient
   to successful Corydoras breeding is patience and
   lots of it.



10. The number of described Corydoras species is now
    around one hundred and forty with many more species as yet undescribed
    and arriving in aquatic shops all over the country almost weekly.
    Because there is a lot of confusion in the true identification
    of many species, especially those that look similar to each
    other C. metae, C. melini and C. davidsandsi are one example.
    C.amapaensis, C. septentrionalis, and C. simulatus are another.
    With these and many other species where there are colour pattern
    similarities, I will In future articles try to demonstrate ways
    of how to differentiate between these and other species.

© Ian Fuller