Breeding Corydoras by surprise

[foxfair]

I don't consider myself as a breeder, so the title says it right: I did it by surprise most of the time.

I have a 55 gallons community tank, 6 Corydoras trilineatus (NOT the true Corydoras julii even they were sold under this name, most LFS and even Aqua huna make the same mistake), 5 male and 1 female and lots of mollies in the tank. This tank was established for about ~2 years. They have lived in the tank since I started.

I was surprised by a tiny cory juvenile on a weekend afternoon, apparently there were some spawning actions I missed, and somehow this brave young one has survived. On the next day, I found another one which was even smaller. I briefly guess the time difference between these two juveniles is about 2-3 weeks. So I start paying more attention to how these Corydoras fish are doing, especially their spawn action. I usually do a weekly 30% water change, so I started checking them after the maintenance. I did trigger their spawning behaviors after the first water change, then I collected 118 eggs in the next few hours to the next day. I was excited!!

The hatching procedure was not smooth, I think it was something to do with the water parameters and temperature. I use a Fluval multi-chamber holding and breeding box, which hangs on the outside of my community tank. It took 6 days to see the first fry, unlike the usual 3-5 days I've seen on the Internet. I counted 18-20 fries after 2-3 days, so my setup didn't have a high yield of egg->fry ratio. That's something I could improve in the next round. I fed them Spirulina powder mixed with Aquarium coop's fry food (crush on my palm then mix in the container), then live baby brine shrimps when they were able to consume those live food.

But then something bad happened: It was 12 days after the first fry spawned. I found all newborn cory babies dead but only two were still alive in the morning. Granted that I did add some sand substrates on the 9th day, but I don't think sand would impact the water parameter so much to take down almost all baby Corydoras fishes. One died the next day, so all I have is now a single survivor for this batch. I was upset but didn't know what went wrong, the only thing I could do was a daily 30-50% water change for a week. Added a canister filter to power the filtration effect up and hopefully bring more bacteria in. Daily water change seems worked, because they spawned again in 6 days after the big incident happened. I was relieved to count 122 eggs at this time, but I separated them into two breeder boxes. From here, I started doing 50% water change every two days. And I still keep monitoring the water parameters with test strips and the API test kit. I also raised the water temperature from 72 to 78F gradually . The first fry hatched after 3 days, so I think the temperature and water condition control did help. Exactly one week later, the big Mama spawned again with 168 eggs(!!). I guess she starts getting familiar with the spawning cycle and does an excellent job.

So now, I have 3 breeder boxes with lots of fries I couldn't count the number, but I only spotted 1-2 dead babies in the past two batches. The first brave survivor is a miniature of their adults now. I also add 3 younger Corydoras trilineatus bought from LFS, hope to add a female and release the spawning pressure of the big Mama. But I do not know if there is actually a female in these three, we shall see in a few months when they grow up. I still need to figure out how to set up a grow-out tank (a 10 or 20 gallon tank would be nice) with limited home space. I'll report back with future updates.

 

The following picture: R.I.P. The first batch of baby fries, only one has survived. 

 

 

 

Edited August 14, 2023 by foxfair

[foxfair]

Spawning actions and eggs in the second batch.

 

 

[nabokovfan87]

On 8/13/2023 at 10:15 PM, foxfair said:

 It took 6 days to see the first fry, unlike the usual 3-5 days I've seen on the Internet.

It can take anywhere from ~2 days up to 10 days.  It's all variable.  There isn't a hard and fast rule.

Congratulations on the colony expansion though, that's really cool.  It's one of my favorite things is seeing a baby corydoras just appear.

Welcome to the forums 🙂

[foxfair]

On 8/13/2023 at 10:41 PM, nabokovfan87 said:

It can take anywhere from ~2 days up to 10 days.  It's all variable.  There isn't a hard and fast rule.

Congratulations on the colony expansion though, that's really cool.  It's one of my favorite things is seeing a baby corydoras just appear.

Welcome to the forums 🙂

Since @nabokovfan87 is here, I forgot to mention that I set up a quarantine tank for Corydoras schultzei (black cory), which was partially inspired by the video of his bigger tank with black cory. I decided my second Corydoras species would be it. I bought these black cory from two different sources. I believe I saw two female when I put them into the tank, but I don't think they are mature enough to start spawning. So they have stayed in this tank for past three weeks. Today I did a regular maintenance (30% water change) and guess what I found? Eggs on the wall. They are not sticky anymore, so I guess they must be over the first day mark. There are at least 3 places with a bunch of eggs. I spot checked and some of them are unfertilized in white color. I don't want to move them because I wasn't sure about the spawn time. Let's see if any of these eggs could hatch and bring us another surprise.

 

 

 

 

[nabokovfan87]

On 8/13/2023 at 11:12 PM, foxfair said:

Since @nabokovfan87 is here, I forgot to mention that I set up a quarantine tank for Corydoras schultzei (black cory), which was partially inspired by the video of his bigger tank with black cory. I decided my second Corydoras species would be it. I bought these black cory from two different sources. I believe I saw two female when I put them into the tank, but I don't think they are mature enough to start spawning.

I'm definitely excited!  I need all the help I can get on spawning these ones! I tried to setup the same exact thing originally, ended up losing far too many. I'm looking forward to adding more once I can sell some (and then add in a new batch).  I got mine originally off of aquabid from 2 different sellers.

 

On 8/13/2023 at 11:12 PM, foxfair said:

Today I did a regular maintenance (30% water change) and guess what I found? Eggs on the wall. They are not sticky anymore, so I guess they must be over the first day mark. There are at least 3 places with a bunch of eggs.

That's awesome. One bit of advice I watched recently was about how they like new surroundings and that tends to trigger them as well.  Whenever I move them to a new tank they definitely get a bit more active.

I'm excited for you, waiting for the journal! Congratulations on the colony and hopefully they both do well for you.

[foxfair]

On 8/14/2023 at 12:30 AM, nabokovfan87 said:

I'm definitely excited!  I need all the help I can get on spawning these ones! I tried to setup the same exact thing originally, ended up losing far too many. I'm looking forward to adding more once I can sell some (and then add in a new batch).  I got mine originally off of aquabid from 2 different sellers.

 

That's awesome. One bit of advice I watched recently was about how they like new surroundings and that tends to trigger them as well.  Whenever I move them to a new tank they definitely get a bit more active.

I'm excited for you, waiting for the journal! Congratulations on the colony and hopefully they both do well for you.

I got mine from Flip Aquatics' website which I bought cherry shrimp before, and JDAquatics on getgills.com. I do check aquabid frequently but I am not sure how sellers will pack and ship. One interesting thing I found out was black cory likes playing dead when the environment was changed suddenly. Yesterday I spotted a black Cory showed its belly up for ~5 minutes in the bottom of the tank, and others were stopping on the java ferns without any movement too.

I don't plan to breed Corydoras schultzei in a short time, maybe wait ~5-6 months until they're all mature, but I also welcome any surprise before that.

 

[foxfair]

Just got another round of eggs this evening. Because I moved these black cory from the quarantine tank to my community tank, I am not sure if these are purely false julii cory's eggs, or a mix of them and black Cory. I did find some eggs are in different size and shape than others, so I assume I have both. I did not take any photo while rolling eggs out of java Fern leaves, and only found ~5 on the glass and one was at the intake of a canister filter (lol, good save for a cory's life).

I tried to identify which female (black Cory) was the candidate for spawning, but I couldn't tell because they are still young. Anyway, I pulled all 80ish eggs out of the tank and moved them to the breeder box.

I assume ~4 weeks later I will need to start looking for a new grow out tank due to recent spawning batches, I did release the first juvenile back to the community tank. Even with 3 breeder boxes I kind of feel the pressure of their living space.

 

[foxfair]

Breeding log of my Corydoras trilineatus (false Julii Cory or Leopard Cory):

[Water parameter]

pH: 6.4

Temperature 72-75F

ammonia: 0-1.0 ppm

nitrite: 0 ppm

nitrate: 20-60 ppm (60 was before water change)

TDS: 80-160

GH: 5-6 drops

KH: 2-3 drops

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[Trigger condition and spawning behavior]

Spawn was usually triggered by an environmental change, for example a weekly water change of 30% - 50% range would work. Add tap water with the temperature lower than the tank (-2 to -5 degrees F). A few hours later, observe these cory's activities especially if any of them focuses on cleaning leaves of java ferns, swims rapidly in groups and/or digs into sand substrates. I have only one mature female and the rest (5) are all male, but only 2-3 males anticipate spawning behavior. Before and after the famous T pose, the female holds 1-2 eggs in her pectoral fins like us holding something in our hands. Then she will find a spot to place eggs. Mostly on the java fern leaves and roots in my tank. I only found less than 10 eggs laid on glass surface and other places in the past 3 spawns. I know some species of Corydoras will give more eggs in each round, but I only see 1-2 eggs from the female Cory. Also it seems like she likes laying eggs on leaves more than glass surfaces.

 

The stickiness of these eggs (based on my past experience of pulling eggs by fingers):

• 0-1 hour: Very sticky, the egg shell (or exteriors?) feels softer and you can see a ring of sticky slime (I don't know a better way to describe it) around each egg when placing them on the transparent wall of a breeder box. 
• 1-4 hours: The 4 hour mark is my own rough assumption of the most recent spawning cycle in their activities. The egg shell is harder than the first stage, You can apply pressure to roll it on / off a surface without worrying if it's gonna break. Overall it is sticky enough to move around fingers (thumb to index fingers, left to right hand etc) and different material of surfaces (java ferns, human skin to plastic of breeder box) but still maintain the same stickiness level.
• 4+ hours: If you pull an egg from point A to B, simply roll your fingers then the egg falls into the water without too much effort, or you have some problem to place it on the wall then it is in this stage. It is between none to a little stickiness depending on the time being laid on the first surface. Stickiness level is not maintained, or it just degrades quickly, I.e. when you pull an egg you feel it is sticky and stays on your finger, but it cannot stick on a smooth surface when placing it in a breeder box. I would say the egg shell is hardened more at this stage, and I usually would not move eggs at this stage - just leave them wherever I found them . 

===============================

[How many eggs in each spawn]

These are the most recent spawns I collected:

• 118 eggs on Jul 4.
• 122 eggs on Jul 28.
• 168 eggs on Aug 4 - exact one week after the above spawn.
• 89 eggs on Aug 16 - could be a mixed spawn.  I don't know if these eggs all came from the same mother or not, because there are some Corydoras schultzei (black Cory) in the same tank. I didn't check the whole tank just pick whatever I could see up, so I believe there were unknown numbers of eggs which are still in the tank.

(I still need to measure the egg size in diameter -- to be filled later)