Corydoras Aenus - Do Fry Move While Absorbing Yolk Sac?

[esquirette2007]

Hi,

My bronze corys have been spawning for many months now. Finally bought a tank separator (with holes, so has same tank water) so that the next time they spawned, I could move them into the isolated section.

A few days ago I could see them begin spawning, and moved the female and the male that seemed most interested into the spawning area, and ended up with 200+ eggs. The next morning the parents really wanted to get back to the group on the other side of the clear separator, so back they went to their happy group.

About 99% of the eggs hatched 2 1/2 days later (yesterday). They flitted around a little bit, but not much movement, when they first hatched (I watched for hours, it was so fun!). But this morning (1 day after hatching) there is no movement at all that I can see.

The substrate was the same natural fairly large gravel that's in the tank. I saw a fry through the glass that was trapped in a space under the gravel rocks.

After reading the board, I read that the fry are not free-swimming for a few days while they absorb their egg sac. Do they move while this is happening? I can't see them, as they blend into the gravel, unless they swim upward out of the gravel. If they don't move while absorbing the sac, maybe some have survived.

So, can someone tell me how they behave before they're free-swimming? Then I can start my process of elimination as to what went wrong or if I should wait.

Thanks,

Karen

 

[mlawson]

I'll tell you how I breed Corydoras Aeneus.

I put six mature specemins into a 10 gallon tank with a sponge filter. I condition them on live foods and high quality flake and pellet food prior to spawning. If they are reluctant to breed I carry out a 50% water change with cold rainwater, bringing the temperature down to 17 C. This normally triggers spawning and it is interesting to watch the male persuing the female. Once all the eggs are laid around the tank. I leave them for 24 hours. I then place a clear plastic container within the tank at the top and put some of the tank water in. Here I place the 1 day old eggs, and airate softly. I also add some fungus treatment and carry out daily water changes of 50%.

It should take another 2-4 days to hatch and I remove any unhatched eggs. At this time I begin starting up brine shrimp cultures and infusoria, also some microworm. It should take 3 days for them to use their yolk sac. And they normally don't move when they still have their yolk sac. They should be free swimming after a further 3 days and I feed them infusoria 3-4 times a day, careful to change water after meals. After a week I feed some infusoria, microworm and liquid fry food and start up some brine shrimp culture. I then feed them mainly on BBS and crushed flake.

Cheers,

Mike

 

[jollysue]

I would get rid of the gravel in the fry tank next time. A bare bottom will work best. They need clean quarters and can easily get fungus or bacterial infection, and then they die very fast. It will be very hard to keep them clean with the gravel.

 

[Bozza]

Ive read in places, and some people i believe have said to have some sand on the bottom of the tank works good. I don't believe in bare bottom tanks, its more prone to disease then have some sand/gravel on the bottom. Also don't the fry become deformed because they are growing up on bare bottom tanks? Not sure if thats true or not

 

[jollysue]

I am addressing the issue of hatching fry. I have never heard of a problem with fry on bare bottom tanks. When the fry are in the hatching stage they need a very clean bottom, as they are in danger of fungus. That means no left over food that could deteriorate. It must be removed daily, or be where it gets washed away like in a net. The tiny fry are very easily hurt or lost during these frequent cleanings. Gravel would be really difficult to clean. Once they are big enough to plow sand, then they can have sand added or be moved to a grow out tank. They also can damage the next harvest of eggs at that point, so they are ready to be moved. I just released mine into the parent tank.

I do not put a deep substrate in a tank that will not be planted. It is not necessary, and it is a source of deteriorating matter that can become a problem. The Cories particularly don't need a deep substrate, and they do need a clean bottom. Sand that is not planted can release poison gases from dead matter. Food goes deeper than the cories can dig.

If anyone is using substrate for the hatching tank, I would be interested to hear about it. Neon may have substrate, because he is hatching in the parents' tank. My bronze offer up volunteers regularly, and there is a light covering of sand in their tank. But only one or two will survive and grow up hatching on their own in the parents' tank w/o a net.

 

[mlawson]

I would never use gravel in a cory breeding tank. Either use no substrate or a layer of thin sand.
My method is strange in that I move the eggs. I don't like bare tanks, even for breeding. My corydoras breeding tank is strange as it has quite a thick layer of Eco-complete planted aquarium substrate. This means I can keep it planted with a good bottom and there is no accumalation as Eco-complete contains beneficial bacteria. I move the eggs because I get better hatch results. The corys sometimes nible on the eggs and I can change water and add fungus treatment more easily. If you attempted to breed them without moving the fry I would sugest having no substrate but a few caves and potted plants.

Cheers,
Mike

 

[Corys4u]

u are best off having some form of a substrate in any tank. be it a breeding tank or not. there is an increased chance of infection in the barbels on a plain glass bottom tank than one with a substrate. i know that many top breeders cant speak enough of having a sand substrate in a tank with corys in it.

 

[Coryologist]

If anyone is using substrate for the hatching tank, I would be interested to hear about it. Neon may have substrate, because he is hatching in the parents' tank. My bronze offer up volunteers regularly, and there is a light covering of sand in their tank. But only one or two will survive and grow up hatching on their own in the parents' tank w/o a net.

Greetings. I am currently running 96 tanks. I had 320 tanks at the old hatchery. I have never had sand or gravel in any of my tanks. I have never experienced any negative health effects from not using any substrate. I have never raised a Cory that was born in my tanks that had so much as a single missing barbel from bacterial infection. I did, 2 weeks ago, put some play sand in a 10 G. tank of C. weitzmani juveniles, to see if it would change their coloration after being raised in a bare-bottomed tank, painted black. It did not change their coloration afer 2 weeks.

While I never use substrate, I believe my good friend Ian has substrate in all of his tanks. He's a better man the me. I would find it impossible to clean 100 tanks with subtrate. I don't know how anyone does it. It's important to understand that most of my fish-keeping regimen was developed over 50 years of raising guppies while trying to fit Corys into that same work flow. It works for me, but I believe that there is more than one way to do amything. It may not be as easy or as successful, but we all have to work within our abilities. If you are going to raise fry in a bare bottomed tank, the bottom must be kept meticulously clean by scrubbing it at least once a day with a camel hair paint brush, right before you do your water change.

Now, with all of that being said I will state that if I had my druthers, Id have play sand in all of my tanks. I've yet to hear of a discovery in the Amazon River of fish found on a glass bottow. We shoud always strive to give our Corys as much of a natural biotype as is feasible, with feasible being the key word. As much as I love to see those juvies plowing through that sand, if I had to clean 100 or so tanks with substrate, I'd rather take up stamp collecting. But that's just me.

Warning: Your mileage may vary! - Frank

 

[jollysue]

If anyone is using substrate for the hatching tank, I would be interested to hear about it. Neon may have substrate, because he is hatching in the parents' tank. My bronze offer up volunteers regularly, and there is a light covering of sand in their tank. But only one or two will survive and grow up hatching on their own in the parents' tank w/o a net.

As much as I love to see those juvies plowing through that sand, if I had to clean 100 or so tanks with substrate, I'd rather take up stamp collecting. But that's just me.

Warning: Your mileage may vary! - Frank

Of course, Frank, those ideal natural biotopes don't produce as high a survival rates as our methods.

As I mentioned, I have just released fry an 1/8th of an inch or less w/o the tail into the parents' tank which has a thin covering of sand. It goes bare in spots where there is lots of current or activity. I have three Cory only tanks that have a sparse layer of sand (this is what was recommended to me when I set them up by Inchworm). They can easily reach the food and keep it eaten--except for the cunning black worms that dig in under the driftwood. I have only been keeping Cories that way for a year and a half. Still I have never had a bacterial infection in any of my Cories' barbells as far as I know.

When I tried hatching in a small separate tank I had lots of battles with fungus--didn't know about Maroxy yet--and lost lots of fry to my carelessness during cleanings. (They went out with the water change, or up the syphon and down the drain, etc. I would bleary eyed blindly forget to put the water in a bucket first. grr) I have had no trouble with fungus in the net, and I only lose fry when I accidentally wash them out too soon. I am getting better with that--experience

 

[Coryologist]

When I tried hatching in a small separate tank I had lots of battles with fungus--didn't know about Maroxy yet--and lost lots of fry to my carelessness during cleanings. (They went out with the water change, or up the syphon and down the drain, etc. I would bleary eyed blindly forget to put the water in a bucket first. grr) I have had no trouble with fungus in the net, and I only lose fry when I accidentally wash them out too soon. I am getting better with that--experience. "Quote edited by Coryologist."

Hi. I tried hatching eggs and raising fry in 2.5 USG tanks, with mixed success. I hatch and raise all of my Corys in 10 USG tanks and am fairing much better. Less chance for water parameter fluctuations. Additionally, I now refrain from using any commercial antifungal agent as they will also kill any beneficial bacteria in your sponge filter which is my primary first food sources for my wigglers. A fresh squeeze of a well-seasoned sponge filter will supply your Corys with all they need to get a good start. I start small squeezes about a day before most have absorbed their yolk sac. I have never used a breeding net, other than for guppies and only then on rare occasions - so I can't offer an opinion on that.. Hey, I've only tried a spawning mop one time in my career and they have been banished from my fish room. Just not workable in my situation as I feed more heavily than most people I discuss the subject with. Probably why I haven't spawnded more species, but I'm OK with that. - Frank

 

[esquirette2007]

Thanks so much everyone for sharing all of your tips and techniques. You guys are great! I'll eventually get it right.

So, ever hopeful...

Mike, Do I understand your post correctly that the fry don't move for 6 days? You said 3 days to absorb the egg sac without moving, then a further 3 days before they're free-swimming. Is that 6 days of no movement?

Thanks,

Karen

 

[Coryologist]

Do I understand your post correctly that the fry don't move for 6 days? You said 3 days to absorb the egg sac without moving, then a further 3 days before they're free-swimming. Is that 6 days of no movement? Thanks, Karen - Quote edited by Coryologist.

Hi. I think you may have misunderstood what was being said. From the moment Corys hatch they go through periods of inactivity, followed by much scurrying around. Sometimes I'll think a wiggler is dead from being in a weird position, like upside down. A gentle puff from a turkey baster has it right side up and scurrying about in no time. The term "free swimming" simply means that the fry has fully absorbed it's yolk sac and now must search for food. This generally takes place within 3 to 5 days. I hope this helps. - Frank

 

[esquirette2007]

Hi Frank,

Awwww shucks. How depressing is that - to have lost 200 corys. Wah. So, nix on the gravel. I'll try one of the suggestions above next time.

Oh, and how do you clean the bare bottom tank with the camel hair paintbrush without hurting the miniscule fry?

Thanks,

Karen

 

[Coryologist]

Hi Frank. How do you clean the bare bottom tank with the camel hair paintbrush without hurting the miniscule fry? Thanks, Karen.

I can assure you, if you are very careful, you won't hurt a single one. I never have and I really do a thorough job. It's not a perfect world. If a few die so that many may live, that's acceptable. Remember, in nature, they say that 1 in 100 survive to adulthood. I can assure you, if you are careful and observant you won't hurt them. - Frank

 

[Cl@ssy Burd]

Blimey i must have just been lucky when my peppers spawned in my communal tank and 1 naturally survived then.

Never knew anything about it until a water change one day produced a mini pepper lol