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Discussion Starter · #1 ·
I have some Sterbai corydora fry that I am attempting to raise for the first time. They are currently about three weeks old and it is going well so far. I cannot get an accurate count, but there is about 30 of them of various sizes. I have them housed in a divided 10 gallon tank (so, 5 gallons) with a sponge filter. They are still pretty small now and I am not sure if I should be netting them up this early, but I know I'll have to spread them to others tanks some time. I am wondering when would be a good time to move them out of this tank or how many I should have in one tank?

If anybody has experience raising corys and has any tips they can share that would be awesome too!
 

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Who is in the other tanks? Since I'd think one factor is going to be how big the cory fry need to be in order to not to get eaten. Are they big enough yet not to fit in their future tank mate's mouths?
 

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At least one seems to be considerably larger than the rest. As soon as they're large enough to not be eaten, they can go back into the main tank, and you might want to do that now with just the biggest few if you have somewhere they won't be eaten. You're fine for now as long as the water is clean, but they're going to get a bit crowded in there when they start growing in earnest.
 

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Discussion Starter · #4 ·
At least one seems to be considerably larger than the rest. As soon as they're large enough to not be eaten, they can go back into the main tank, and you might want to do that now with just the biggest few if you have somewhere they won't be eaten. You're fine for now as long as the water is clean, but they're going to get a bit crowded in there when they start growing in earnest.
Yeah. It's strange how some of them are growing so much faster than the others. I have a couple that are over an inch and some that are still tiny and translucent. The combination of fry in there are from two separate hatchings but they are, at most, a week apart.

Who is in the other tanks? Since I'd think one factor is going to be how big the cory fry need to be in order to not to get eaten. Are they big enough yet not to fit in their future tank mate's mouths?
Ha, that's a fine unit of measure! Unfortunately I don't have room to keep these long term. I might keep a few but the others I plan to sell to the local fish shop. There just isn't enough room for these guys in the tank with their parents.
 

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I find this true with even large fry/juveniles.
I keep my grow out tanks for the best specimens and put the others in the community tank with swordtails and danio. The ones in the much smaller grow out tank, grows much faster than those sharing with adult fish.
Also it is hard to feed the many small meals young fish need, without overfeeding the other fish.

If needs be, think outside of the square, a large cooler or plastic tub works just as good for raising fry.
 

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You should feed 4 ( small ground up food) times a day and do 50% water changes this will help keep the water pristine and also when doing water changes gravel vac with just a hose. Have been breeding cory's for years now.

Egg yolk is a excellent food source.
 

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Discussion Starter · #9 ·
You should feed 4 ( small ground up food) times a day and do 50% water changes this will help keep the water pristine and also when doing water changes gravel vac with just a hose. Have been breeding cory's for years now.

Egg yolk is a excellent food source.
I have been feeding three times a day because that is most convenient for me right now (lunch break, right after work and before I go to bed). I have been hatching brine shrimp in a couple two liter hatcheries and feeding them that. The fry don't seem to want to eat the ground shrimp pellets or first-bites that I have tried to give them. I think I might be overfeeding them though because I am dealing with an outbreak of hydra at the moment. Never had that problem before. I blame the brine shrimp but I don't really know.

I moved the biggest dozen or so fish to another tank.
 

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If you have a green swimming pool or old pond with lots of living things like tadpoles or daphnia, get a bucket full and keep your small fry in that. This helps them develop good intestinal microbes and you will notice they respond better to the same amount of food as fish raised in sterile water. They just have to live in green water until going after micro food is no longer energy efficient.
 

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Yeah. It's strange how some of them are growing so much faster than the others. I have a couple that are over an inch and some that are still tiny and translucent. ... I might keep a few but the others I plan to sell to the local fish shop. ... I moved the biggest dozen or so fish to another tank. ...
It's not strange, it's natural, literally natural. The more spawns you raise the more you'll see that. Those that mature the soonest pair off the soonest and reproduce the soonest. Natural selection is less concerned with colors/finnage than it is with maturity rate, the opposite usually holds true with artificial (human) selection. From the dozen that have been removed try to identify an alpha and beta pair, those 4 fish you keep. The rest sell, even as juveniles. That's natural selection. If you are targeting a particular color/fin type (artificial) than you'll need to raise them all to sexual maturity, as the flashiest fish have a tendency to mature the latest.
 

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Ditto, I find it easier to select good stock after 6 weeks than at 3 months where they start to nearly catch up to each other....
But the "alpha fish" will always be that little bit bigger and more dominant. One way of getting the colour to come out, is to stunt the fish.... bad idea. but I have two tanks full of examples of fish born 5 days apart.

The big ones are still pretty pale, (rainbow platies), the small ones, a 3rd their size, are just about fully coloured up already... but they are retards. (it was an experiment that went a bit far, but now I know the importance of initial food sources as well as keeping water conditions pristine).
 

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Growth rates of fry are pretty much based on the food consumption. More food, more nutrition, faster growth.

Female corys do grow faster and remain larger than males.

The big cory is just a food hog (out"competes") and is probably a female.
Just make sure all the fry are getting their fair share to have similar growth results.
You can try feeding Repashy Spawn & Grown gel food. Just throw a nice sized gel block in so there's enough to last for everyone to get their bellies full, not just the fast eating behemoths. Supposed to be water stable for up to 24 hours before fouling the water.
 

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They only start to catch up to each other in our tanks, where they have access to an uninterrupted ample food supply. It's not like that out in the wild.

The "alpha fish" will always be that little bit bigger and more dominant in our tanks, for the same reason. In the wild there are alpha fish and dead fish. The colorful stunted fish never happen, they get dead first.

Big ones, i.e. the first to sexually mature, can be paler if the color(less) trait is advantageous to survival. Albino fish, as an example, don't occur naturally. It's us humans who peer into a grow out tank and amongst hundreds of nearly identical fry find our eyes gravitating to the one(s) that stand out the most. Predators in the wild also peer into waterways and identify flashy fish, and quickly cull them.

Different survival traits can go hand in hand. Small rainbow platy, that naturally are not supposed to exist, can also lack other traits that their relatively large pale siblings have, such as mental acuity (as you so eloquently state). :nerd:
 

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Yeah, I feel like a worm, the tank was not in easy reach and was running unheated and with very little light for the first 6 weeks or so.
The fish from that tank are all weird, they even swim strange because of disproportionately large fins. But, there are three really nice colour variant fry between them with a much redder hue over their metallic bodies.
I should probably cull the whole tank, but my heart is too soft. I have always ended up keeping all the slightly deformed fish.... just away from the opposite sex.
 

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Discussion Starter · #16 ·
Lots of great information here guys! I am starting to find that breeding fish is more compelling than taking care of plants, at least for me anyways. It is interesting to see the effects of genetics and environment on the fry as they grow. As these cories are getting bigger I have lost a few for unknown reasons and I noticed one fish that is missing an eye (completely healthy otherwise). I guess that the few deaths are probably just the natural selection process eliminating the weaker fish which is a good thing for a healthy gene pool. I don't see any reason to kill the one eyed fish and I don't really want to... Is a physical defect like that something that can be passed down to offspring?
 

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... one fish that is missing an eye (completely healthy otherwise). ... I don't see any reason to kill the one eyed fish and I don't really want to... Is a physical defect like that something that can be passed down to offspring?
Some of its offspring may be born normally some may be born with one eye. Under the auspices of human keepers we could find out. Nature however isn't so forgiving. A one-eyed fish would fall prey to a bird, turtle, snake, larger fish, etc, long before it reached sexual maturity and so its genetics, both good & bad, would never have the chance to manifest themselves.

Case in point: Many waterways in North America contain feral goldfish. For the most part they do well in evading predators and grow to impressive sizes that could never be attained in aquariums. But these are fish with no deformities. We don't see any Calico goldfish in wild waterways. Calicos, fancy guppies, fancy bettas, the list goes on ad nauseam, are deformities that humans intentionally propagated. But I digress.
 

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If you have a green swimming pool or old pond with lots of living things like tadpoles or daphnia, get a bucket full and keep your small fry in that. This helps them develop good intestinal microbes and you will notice they respond better to the same amount of food as fish raised in sterile water. They just have to live in green water until going after micro food is no longer energy efficient.
Do you think green water is good for alabino cory fries? Thanks.
 

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The green water might not do much, but small animals feeding on the algae do. Not sure if it is the best thing to do if you have the fry in the same bucket, but 24 h ligting and a bit of tertilizer would make the algae explode. If the water clears up, there should be LOTS of food in the water for the fry.
If you can get hold of a culture of microworms, I would go for that instead.
 
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