Food-a limiting factor for breeding"problematic"Corydoras?

[cartouche]

Someone of you know that more than one year ago, I posted here a request for help, because I intended to breed Corydoras hormonally. My questions then raised a lot of aversion, some people accused me of not being a "right breeder", and recommended me to make repeated "natural" attempts over and over again, virtually until the Judgement Day. In the meantime, I mastered hormonal breeding very successfully, although during my early experiments - knowing virtually nothing about the procedures and dosing - I had to get over the loss of some valuable fish. However, we have a folk saying "Everything bad is good for something", and thanks to this experience I largely resolved a mystery, why the breeding of "problematic" Corydoras species (e.g. reticulatus, robineae, sodalis, schwartzi etc.) is so difficult in captivity. I also saved many years of my time, because if I continued in my "natural attempts", I would probably continue uselessly and unsuccessfully until my natural death.

The reason is surprisingly simple: The fish produce no eggs. Even with a high-quality diet contaning lots of essential fatty acids and nutrients (earthworms, tubifex, beef heart, mayfly larvae, bloodworms, daphnia), I was not able to feed them into breeding condition. In fact, after nearly two months of very heavy feeding several times a day I injected a group of C. schwartzi, and the plumpiest female that then unluckily died had only ONE ripe egg. Subsequently I made similar experience with other "problematic" species, although I try to feed them well all the time (mainly with earthworms, beef heart and plankton). Despite massive feeding, only few females became noticeably volumnuos, and even then, they didn't react to hormonal stimulation at all (except some activity that lasted several hours, but produced no eggs). This concerns all "problematic" Corydoras that I have - reticulatus, schwartzi, loxozonus, robineae, sodalis. Actually only Loxozonus produced two infertile eggs after I injected my whole breeding group of ten fish. At the same time, it is surprising that other three imported Corydoras species that I have (C03 deckeri and two variants of alleged "Napoensis"), can be fed very well even with relatively simple food and can be spawned both naturally and hormonally (with Napoensis producing hundreds of eggs). Not speaking about my imported Corydoras similis that spawned regularly together with my Sterbai.

Although I admit that this my explanation may not be complete, because some people allegedly bred C. schwartzi and C. loxozonus by chance with ordinary food, I suspect that these "problematic" species may need something that we can't accomodate them in captivity. Currently I think over to get rid of the majority of these fish troublemakers, because they are not worthy of the money that I have been uselessly expending on them for several years already, so I have no problems to share my experience with you. I will probably only concentrate on Reticulatus and Robineae that I like most.

[CoryWally]

Hi Cartouche,
I'm not exactly sure where you are heading, but I gather from your post that hormonal injections were not entirely successful in your attempts to breed some difficult species.

Personally, I try to provide my corydoras, and other fish with optimal conditions in an attempt to breed them. I do not necessarily subscribe to simulating dry seasons or drastic shifts in water parameters. All my breeding groups consist of small adult groups of between 6 to 10 individuals in their own 15 gallon tank. I do not think mixed species groups respond so well. Food, I believe is very important. Like you I try and provide a varied diet of live, frozen and quality manufactured food. Regular weekly 50% water changes and a close eye on pH keeps tabs on water quality and chemistry, for me at least.

Using this basic fish-keeping mantra, I have bred over 20 species of corydoras, aspidoras and scleromystax plus a number of loricarid species in the last three years. Obviously, some species are more difficult than others and will be more rigid to their owen seasonal clocks, hence, some species will only breed during a short period corresponding to their natural instincts.

In essence, good food, low stocking densities, good water conditions and the correct population dynamics (including ratios of M/F) will provide the fish with as much as we can give them, after that it's up to them to either respond or otherwise. I have come across species which stubbonly refuse to spawn and after giving them the best conditions for 18 months or so, I'll move on to something different.

There are some species which suit intensive aquaculture and some which I believe do not. I can produce hundreds of barbatus, pandas, axelrodi etc with the same effort as producing half a dozen araguaiaensis or weitzmani for example. I'm a hobbyist so am happy to take the time and effort to produce a few dozen youngsters from a hard to breed species to distribute around. At the same time, I make a few quid from bread and butter species to pay for the heating.

Good luck with your breeding efforts,
Mark.
I

[cartouche]

Well, my attempts with these species were not successful, but hormonal injections have nothing to do with it. If a fish is full of eggs, it must spawn after hormonal stimulation. With the use of hormones, I breed several "less problematic" species of Corydoras regularly. It is much easier than sophisticated changes of water, temperature and/or chemistry. The problem is that the "more problematic" fish refuse to spawn because they have no eggs. Hence nothing - including hormones - can help me. I know that some English posters here are allergic to hormonal stimulation, but it is a common, widely used method for industrial breeding of fish in some European countries. So far I haven't heard about Greenpeace complaining of it at UN.

Believe me that the "natural" stimulation of some difficult Corydoras is a waste of time. I actually decisively turned to hormonal stimulation after I got a reply from a breeder, who reported an accidental successful breeding of Corydoras robineae in the internet. I asked him, how successfuly he continued in the breeding of this species, and he said that his further attempts desperately failed, both in adults and the F1 generation. After several years, he got rid of all his Robineae, because they only uselessly wasted place in his fishhouse. So much to the "natural breeding" of difficult Corydoras.

[Mike_Noren]

You wont get mature eggs and sperm in fish which need a specific environmental trigger to have their gonads ripen, regardless of what you feed them.

Didn't your hormone injection kit come with instructions? Usually they're sold with complete protocols for the species you're trying to breed.

[CoryWally]

Hi Cartouche,
I know how you like a good discussion, but I'm still not sure where you're heading.

You are obviously sold on the idea of hormonal stimulation so there's no argument to be had there - some will agree, others disagree.

As for sophisticated water changes etc, this is just good animal husbandry designed to provide optimum conditions and bring fish into condition, when they may or may not spawn.

Have you tried a centralised system, containing easily bred species and more difficult species? This is a well documented method to promote multiple spawnings, often of hard-to-breed species. Although I have separate tanks, I often transfer water from a tank of spawning fish e.g. barbatus to a tank where closely related fish are ready to spawn, but need an extra stimulus, e.g. C113's. A single pair of barbatus can produce 600 eggs a month and my C113's do 100 a month. That should be sufficient to keep the U.K. supplied with both these species permanently imo.

Unfortunately, as long as hard to breed species are readily available from the wild at a cheap price (£3 for reticulatus, £7 for robiniae) there is not going to be much of a financial incentive to breed these fish.

Cheers,
Mark.

[cartouche]

You wont get mature eggs and sperm in fish which need a specific environmental trigger to have their gonads ripen, regardless of what you feed them.

Didn't your hormone injection kit come with instructions? Usually they're sold with complete protocols for the species you're trying to breed.

I use carp pituitary. It is the simplest thing, but it works best both in Cypriniformes and Siluriformes (catfish). I actually know a breeder, who bred Schwartzi, Sodalis and Robineae with it. I talked with him about it by phone and it didn't seem that he would have used something miraculous to stimulate egg production in the fish. He work(ed) as a butcher, by the way, and wasn't a particularly sophisticated person. I think the problem may mainly lie in the feeding with live tubifex, which I don't like, however, because it brings many latent diseases into tanks. Furthermore, the imported fish that I bought were adult fish, full-grown. I tried many known or less-known "tricks" before I had injected them - from "stimulating dry and rainy season", changes of temperature, water changes, pH changes, water hardness changes, strong filtration. Nothing worked. Or, better said, from the scarcely bred imported species, actually only Corydoras C03 deckeri reacted well and spawned after a relatively sophisticated procedure, and Sodalis were twice apparently activated.

[cartouche]

Hi Cartouche,
I know how you like a good discussion, but I'm still not sure where you're heading.

You are obviously sold on the idea of hormonal stimulation so there's no argument to be had there - some will agree, others disagree.

As for sophisticated water changes etc, this is just good animal husbandry designed to provide optimum conditions and bring fish into condition, when they may or may not spawn.

Have you tried a centralised system, containing easily bred species and more difficult species? This is a well documented method to promote multiple spawnings, often of hard-to-breed species. Although I have separate tanks, I often transfer water from a tank of spawning fish e.g. barbatus to a tank where closely related fish are ready to spawn, but need an extra stimulus, e.g. C113's. A single pair of barbatus can produce 600 eggs a month and my C113's do 100 a month. That should be sufficient to keep the U.K. supplied with both these species permanently imo.

Unfortunately, as long as hard to breed species are readily available from the wild at a cheap price (£3 for reticulatus, £7 for robiniae) there is not going to be much of a financial incentive to breed these fish.

Cheers,
Mark.

The "tricks" with transferring water (or with the stimulation by the presence of other spawning species) also belong among those that I tried many times. I observed it on my own, because my group of Similis spawned only in the presence of spawning Sterbai. After I removed the Sterbai to other tank, Similis stopped and I couldn't push them to another spawnings by any means (curiously, transferring water from the Sterbai's tank helped only once-twice, but then it failed). However, after I placed them in the tank with spawning Sterbai, they began to spawn again. Yet in other species this method didn't help at all.

I must add that Barbatus also belong to my "problematic" fish. I have no problems to spawn them (in fact, they spawn like crazy) and fertility rate also seems high (judging from the % of white eggs the next day), but after two days, at least half the eggs massly dies from some reason (you can see white points in them). In praxis it means that my hatching rate is maximally 30%. I would say that in about half the cases I get 0% fry, because it is not always easy to recognize the dead eggs from the healthy ones and remove them in time, and the whole bunch is destroyed by fungus spreading from the dead eggs. Since I have permanent problems with dying and fungusing eggs, if I place too many in too small a tank (probably because of the presence of anaerobic bacteria in the air of my badly ventilated fishhouse), I tried to lower the concentration of eggs, but it didn't help at all. I also tried to change water chemistry, from my 8,6 dGH, pH 8 to softer (4-6 dGH), slightly acidic water, but the results were inconsistent. Once I had "good" (i.e. 30%) results, but another time all the bunch perished in the same water. I also suspected that the eggs might be more sensitive to desinfection that I use (methylene blue), but even without it the results were not better.

I consulted it with the breeder from whom I had bought my breeding group, but he was surprised and claimed that he had no problems of this sort and some larvae hatched even in ultra-hard water 30 dGH. I wanted to try even softer water, around 2 dGH, but the fish just stopped spawning. I now think over if the fish may not be somehow damaged - if the breeder used some medications during the rearing, for example. If you didn't have any suggestions, how to solve these problems, I will probably buy a new group of Barbatus and I will see if the problems persist.

[CoryWally]

Hi Cartouche,
A couple of observations with getting barbatus eggs to hatch.

I too had problems with eggs fungussing soon after harvesting. The assumption is that they need soft water (or acidic)to develop and hatch. I tried a number of things including only using rainwater in the hatching tubs which didn't improve things.

I now use tank water which has a pH of around 6.5 and add a couple of alder cones which have two properties - antifungal and they release humic acid. The eggs will be stained a dark brown colour and will usually hatch with a good success rate after 5 days. Another option is to leave the eggs in the parent tank until 24 hours before hatching. Eggs left in the parent tank do not usually fungus. However, the egg membrane will be more delicate and it can be difficult to judge when is best to remove them. Surprisingly, my barbatus don't eat their eggs.

After removal, I always try and re-attach the eggs to the side of the hatching tub. Barbatus eggs are quite adhesive, but very tough so not usually a problem. Plus strong aeration is essential.

I have been using the alder cone technique successfully for the last 2 years and do this for all my corydoras types.

Worth a try before you give up on the barbatus, I suspect their wild habitat is fast diminishing and it will not be long before they are as endangered as macropterus. It would be good to establish this species in the hobby through captive bred stocks only.

Mark.

[cartouche]

Hmmm, alder cones? Where do I get to them? I will have to go to the wood I have some solutio of "humid acids" for tetras, but I haven't tried it in Barbatus yet. I will try to add several drops of it into water, when the Barbatus begin to spawn again. But as I said I think that fungus per se isn't the main cause. I think it is rather a consequence. The eggs simply die after two days from an unknown reason.

[Bas Pels]

although I never bred any corydoras - or related fish, I would - generally speaking - think differently

Many, many aquatic species spend much energy in order to prevent fungus growing before they die. This starts the moment of conception. A factor promoting fungus growth is organic waste in the water.

Fish not coming from water with a high content of organic material might have evolved cutting down their fungal defenses - as the fungal threat is less in their habitat. should we putthese fish in water with a lot of organic waste, they become vunerable for a fungal attack - and especially eggs and fry are sensitive.

Waters coming from gletsjers are typically very pure, while groundwaters in tropic forest areas are brown from all their organic contents. Egg intended to hatch in gletsjer water might never have a chance of hatching in rainforest water, regardless of fertilisation

Personally, I think this is an aspect of our hobby which does not get enough attention

[apistomaster]

I find this a particularly interesting subject for discussion. Not only for "difficult Corydoras species" but some other notoriously difficult to spawn fish. In particular, Symphysodon discus Heckel and Pterophyllum altum. Simply using accepted triggering techniques will not produce results with these species. The problem seems to lie primarily with inducing the females to produce ripe eggs and then proceed with spawning. The males will rather readily spawn even outside their species, especially S. discus Heckel. Altums are more difficult to even grow to breeding size. Much of the Altum problem has to do with the extremely poor condition of the newly imported fish so they never even get off to a good start in tank life.

I have long been considering resorting to experimentation with hormones with some of my pairs of Heckel Discus. I would be sure they were in peak condition and perform the experiments during their normal breeding season which even though they have been relocated to the Northern hemisphere, they as well as many other Neotropical fish tend to spawn in the same corresponding months as the SA rainy (spawning season.) I do not "like' resorting to artificial mean to stimulate spawning but it is a fact that some fish just don't seem able or willing to breed naturally in captivity. Heiko Bleher has told me he knows of no more than somewhere between one and handful of successful Heckel Discus spawns and no true Altum Angels spawns in captivity over the past four decades. Hence there does not yet exist any purebred tank raised strains of these two species in the aquarium hobby.

Perhaps the only way to make a breakthrough and establish TR strains of these and other problematic species are going to require the use of hormones.
The low fertility you are experiencing, Cartouche could be an artifact of timing. If the eggs are not mature or are too old at the time the hormones are administered, it seems to me to stand to reason the that egg viability would be less than if the timing is perfect. These eggs would naturally be subject to microbial attacks regardless of how perfect your water conditions may be. I too have experimented with Alder Cones, peat and the like with varying degrees of success with a wide range of black water species. I have not come to any definite conclusions as to the necessity of doing so.

I have acquired Chorulon, trade name for human chorionic gonadotropin, used in large animal breeding to stimulate ovulation of cattle and horses. For some reason, human derived hormones do not have immunorejection problems as those derived from the same species, according to the Veterinary Dr.
Perhaps a two phase system using one hormone to stimulate production of ripe eggs, then another like the hormones you are using will tilt the balance so a natural spawn can take place with perhaps better fertility rates?

[Coryman]

Cartouche,

Perhaps I have come into this discussion a little late, but nevertheless I would like to pick up on a comment from your original post "because some people allegedly bred C. schwartzi and C. loxozonus by chance with ordinary food," I would like you to ask why you doubt the breeding of these species. Species of which the breeding details have been well documented. In fact I know several people who can breed C. loxozonas to order.

We have covered the hormonal induced breeding thing before and I am not going to get involved with you again on that issue save to say that if we were talking athletics you would be banned from competition. If you were saving a species from extinction then I may relent, but not when financial profit is the only motive.

Mark,
I think a new rule is needed in the CSG Breeders programme.

Ian

[cartouche]

I don't doubt breeding these species. I only state that I can't breed them, because they produce no eggs. I don't know, how these people do it (or, better say, how their fish can do it). I think that I regularly guarantee a high-quality food to all my Corydoras. Still, they can't be spawned by any means in my conditions. Actually, I am glad that I have had the experience with hormonal breeding. Otherwise I would uselessly waste my time with unsuccessful attempts over and over again without knowing the reason of my failures.

As for occasional breeding some "very difficult" species (e.g. robineae or reticulatus), I think we can agree on that they make no practical sense. If someone breeds such a fish once in his life, it has no influnce on its spread in captivity, not speaking about the saving of its natural population. Simply said, things will stay the same like before.