Cory Eggs - Fertile?

Andy S

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Just a quick question - is it possible or is it normal for a bronze corydorus female to lay eggs without the presence of a male? Does this ever happen?
The reason I ask is because I have just 2 bronze corydorus in a community tank with guppies. One of them is pretty large, the other one is smaller. I do not know how to sex them but I'm pretty sure the big one is female, I'm not sure about the smaller one.
A couple of months ago I found about 40 eggs laid in the glass side of the aquarium, I had not observed any spawning behaviour, having said that, I wasn't actually paying too much attention to them at that time; the first I knew was when I was cleaning the glass and there they were. I scraped them off the glass and put them in a small container floated on the water. I put a couple of drops of methylene blue in to prevent moulding. I waited over a week but absolutely nothing happened, not a single egg hatched.
A few days ago the same thing happened but there were now probably 150 eggs. Again I have scraped them off the glass and put them in a floating plastic tub with a couple of drops of methylene blue. I haven't given up hope yet but I see no signs of the eggs developing yet after 3 days.
Is it possible that my smaller fish is also a female and if so is it possible that one of them is just laying eggs without any male involvement? Has that ever happened?
 
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Andy S

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DoubleDutch - Thank you for the prompt reply. I'll leave the current crop of eggs for a few more days and see what happens. I'll also try to get a few more Corys, hopefully I'll have a male and in any case a small group is far better than just two.
 

DoubleDutch

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Correction on one anwer (being fertile if you've two males). That would be unlikely. I expect the smaller one to be male though.
there has been a thread some time ago about a single.Cory laying fertile eggs.
Think that was kind of strange btw
 

FriarThomasIII

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Yeah, get more corydoras. Males are slimmer and smaller, and have pointed fins. Females have rounded fins and are bigger and fatter. If they have eggs then they will have rounded bellies. You'll know that they are mating when they start chasing and reversing the chase and "playing". They eventually form a T shape and start fertilization. Whether they injest the sperm and force it through the gut, of if the sperm is in the water and fertilizes the eggs. No one knows. But then she clamps 3-4 eggs in her rounded fins and sticks them either on the glass or on the underside of the plant leaves. The eggs will get eaten at some point and generally won't live or survive in a community tank. They take about 4 days to hatch, and about 3-4 days to absorb their egg sacs. Then feed them micro worms or exteremely powdered flake or shrimp pellet. In about 2-3 weeks they look and behave like mini adults. When they hit about the 4-5 week mark they are fine to add to the tank. Hope any of this helps.
 
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Andy S

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FriarThomas111 - yes, all information greatly received. Although I only have the two they are what is left of a group of seven that I had a few years ago. The largest is pretty huge and very 'chubby', I'm certain she is female, the smaller one, is far less rounded so maybe I do actually have a true pair.
It may be that there was spawning behaviour, I don't know. They are in a tank I use to grow out guppies and are not in the best location for viewing, I tend to just feed them and do water changes, I rarely get to spend time actually watching them. I haven't given up on the eggs yet although the fact that not a single egg hatched from the last clutch does make me think that maybe none of them are fertile. Time will tell.
 

FriarThomasIII

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My fertility rate was about 30%, so you kinda just have to get lucky. My first clutch never hatched too.
FriarThomas111 - yes, all information greatly received. Although I only have the two they are what is left of a group of seven that I had a few years ago. The largest is pretty huge and very 'chubby', I'm certain she is female, the smaller one, is far less rounded so maybe I do actually have a true pair.
It may be that there was spawning behaviour, I don't know. They are in a tank I use to grow out guppies and are not in the best location for viewing, I tend to just feed them and do water changes, I rarely get to spend time actually watching them. I haven't given up on the eggs yet although the fact that not a single egg hatched from the last clutch does make me think that maybe none of them are fertile. Time will tell.
 
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Andy S

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Oh well, I gave them 8 days and nothing hatched, presumably they were infertile.
 
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Andy S

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Did they change color. Some need 10 days !
No, I saw no change in them whatsoever, a few of them fungused and turned white, I removed them as I found them, the others stayed exactly the same. I even got my magnifying glass out to see if I would detect any eyeing up or similar but there was nothing at all.
 

DoubleDutch

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No, I saw no change in them whatsoever, a few of them fungused and turned white, I removed them as I found them, the others stayed exactly the same. I even got my magnifying glass out to see if I would detect any eyeing up or similar but there was nothing at all.
Ok then they must have been infertile indeed.
 
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