Trying to get Sterbais to breed

[ChrisCook]

I collected a breeding group of 19 Corydoras Sterbai from a seller two weeks ago.
I have tried to induce some egg laying by doing water changes twice a week (25% at a time) but to no avail. I've used quite cold water from the tap (obviously dechlorinated first).

Does anyone have any hints on what else I should try?

A bigger water change?
Water changes on consecutive days?
Changing the tank temperature? (Currently set to 25C)

Any help appreciated

Chris

[MatsP]

So, you have only had these fish two weeks? I'd say, let them settle in before you start messing about with temperature changes, etc.

Mine tend to breed when I've done water changes - I rarely get to keep any eggs, as other fishes eat them before I get to them, as they are in a large community tank. I haven't had any eggs last few water changes, but have one fry collected from an earlier spawn (I had two or three eggs, but only one hatched).

My water changes are slightly cooler, probably dropping temp from 28'C to about 26'C - and they are in soft water, pH around 6.0, TDS around 100 ppm.

There are also plenty of species of catfish that only breed during a certain part of the years, but I remember mine breeding at Christmas last year, so I guess it's not the wrong season at the moment.

Mine were originally captive bred, which does make it a bit easier to breed them in captivity in turn.

--
Mats

[ChrisCook]

Thanks Mats. They've been in for 2 weeks now, so perhaps I am expecting too much too quickly!

[jimoo]

Mine seem to breed year round, and often after water changes. I keep them in a well planted community tank with (probably too many) other fish but still a few seem to make it. Though I think I had these for 6 months or so before they breed the first time.

[Carp37]

Mine actually breed when there's am unintentional temperature spike (increase) in their tank, so a cold water change might not induce them to spawn; I'm sure I've seen somewhere on the web that Ian Fuller breeds his at 82 degrees Fahrenheit.

[cmstwc]

I acquired 11WF last year this time. the first time they bred for me was about 2 months after they settled in my 30G breeding tank. I provide decent among of plants. (narrow leaf java fern) The techniques I found are very useful to induce spawn are: adding a power head (this really works for me); have a big WC (40%) temperature drops from 84-76F (29-24C); feeding live worm after this WC but not prior; using Indian almond leaf (some people argue this, but it works for me); and last thing, patient. Good luck!

[apistomaster]

Thanks Mats. They've been in for 2 weeks now, so perhaps I am expecting too much too quickly!

It would be typical for newly imported wild Corydoras to need at least 2 months of conditioning to get back into excellent health so spawning sooner than that would depend greatly on how healthy they were when you bought them.

It may be slightly harder to induce their first spawn than with tank raised strains but not a whole lot. The basic Corydoras breeding formula of feeding plenty of live and frozen foods along with beginning making cool soft water changes after some period of acclimation to fewer tap water changes will normally induce spawning. Maybe not your first water change so you want to repeat what is a simulation of the dry season with shorter periods of simulated wet seasons. Live worms will be the most helpful food and do allow the water changes to be 6 or 8 degrees cooler than say 82*F. Leave the heater set for 82*f and allow it to raise the temporarily cooler water. The use of the leaves is probably not such a bad idea with the wild fish. The types of leaves mentioned above may help both induce spawning and increase the number of hatchlings. in fact, setting your water to be normalized at 100 ppm for general maintenance then using 50% neat RO water change would probably help your wild fish spawn. There would not be any great benefits to using water much softer than 50 ppm TDS.
I breed Corydoras sterbai in tanks with the water not more than 10 inches deep because the fry seem to do better in fairly shallow water until they transform from larvae to miniatures of the adults. Provide plenty of acrylic yarn bottom mops for additional egg laying locations and to help hide the eggs from predation by the breeders. Spawn the large group then remove them to another similarly set up breeding tank and again for as many Corydoras as you want to raise in total. A group of 3 females and 6 males could produce a few hundred eggs per day per tank in several consecutive days. Left with the eggs for a few days results in egg predation by the breeders. You could easily get up to 1000 eggs from such a group moved from 1 tank to another up to four tanks. You will not raise that many due to infertile eggs and some larvae losses.
Beginners usually raise few more than 25% of the hatched eggs while those with more experience are likely to raise more than 80%.

The existing tank raised strains have become more tolerant of harder water and their lower end can be 100 ppm TDS as opposed to whatever your tap water runs.

[ChrisCook]

Thanks for all the advice