eggs here but

[rfb]

I have had my bronze corys spawn three times now and every time they are unfertalized.This last time they ate them all even though some were not bad ,why is this happening and what can I do aside from remove them.Thanks

[MatsP]

Basic question: How sure are you that you have a mix of males and females? Females have been known to lay eggs on their own, and they will of course not hatch.

Also, nearly all corys will eat eggs and/or fry of their own. Only way to prevent that is to remve the eggs into a floating [1] or net breeder or separate tank (making sure it's got a mature filter and same water chemistry - best way to achieve that is to actually move a filter from the parent tank to the fry tank, along with a quantity of water).

[1] Many experineced breeders use ice-cream tubs and similar.

--
Mats

[apistomaster]

Remove the eggs by sliding a single edged razor blade under them and simultaneously keep a siphon next to the eggs to catch any that may fall off the blade. You can siphon them into the net breeder if you set it in a receiving bucket.

Use some methylene blue in the hatching water to discourage fungus.

[rfb]

I have tried the razor blade with no luck,they just seem to end up looking like scrambled eggs.
I have one male to three females,I just wonder if i mighht need to find another male.

[MatsP]

I would say 2 males to 1 female is the recommended ratio for corys.

--
Mats

[Csababá]

When is it recommended to move the eggs. I mean, immediately after laying or a day later, etc?

[MatsP]

As soon as you see them, I'd say.

I have all my corys in mixed species tanks, so I don't get many eggs due to predation from other fishes, so I will remove any eggs I see.

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Mats

[apistomaster]

When is it recommended to move the eggs. I mean, immediately after laying or a day later, etc?

It only takes Corydoras eggs an hour or so to become firm.
Healthy living eggs do not burst as you slide a single edged razor blade underneath them. Only infertile spoiled eggs burst. You can even pick up a healthy Cory egg with you bare fingers, just like Killiefish eggs.

Moving the eggs is a technique one usually uses when your fish have spawned in a community tank or a Corydoras holding tank. If the tank is set up for breeding then you should only remove the breeders.
I find that Corydoras larvae should be started out in fairly shallow water, 6-8 inches max. You set up their breeding tank partially filled to begin with. This can greatly improve their survival rates.

Some species are so tough and easy to breed that you don't have to worry about the depth of the water although 12 inches is as deep as you should go.
C. aeneus and C. paleatus are able to handle 12 inches of water just fine.

As has been pointed out already, best results come from a 2 male per female ratio.
Young breeder's first spawns are often made up of many infertile eggs but as the fish grow older their fertility rates improve.
Probably some patience will get you through these initial difficulties and eventually you should be rewarded with large sized broods.

[Csababá]

Thnak you very much for the detailed, precise answer.
My aeneus cories (or corys?) laid eggs in the community tank for the third time after the partial water changes but the eggs disappeared after some days for the first time and some of them after a couple of hours for the third time. I was afraid of hurting them with the razor. I didn't know that they can be moved even with fingers. I thought they are strongly attached to the glass.
I'm no too practical (or have read too little) so have one more question. While sliding the eggs how can I collect them? Do thes stay on the razor blade or do i have to siphone them somehow? Sorry for being so unexperienced.

[MatsP]

When I collect Cory eggs, I roll them from the glass (or whatever) onto my finger, and then put them in the breeding container.

--
Mats

[apistomaster]

One of my friends who is quite inventive, built a contraption with a small net and the razor blade attached to scoop and catch the eggs.
I use a simpler method of holding a small siphon hose next to the razor blade to suck up any eggs that fall off the razor blade. It takes a little coordination but it is not that hard. Many eggs simply slip off the glass, adhere to the razor blade and need only be rinsed off the blade into the rearing container.