Raising cory fry; 1-2 deaths per day. Is it normal?

[Karen B.]

Greetings 

My false julii cory laid a lot of eggs and since I upgraded to a 30 gallons, I figured I could raise my population from 8 to 12.

Since I have honey gourami in the tank, let’s just say the females love to snack on the fry. So I got a Ziss breeding box that hangs inside the tank.

I had never successfully raised cory, and so far they are 1 week old so I am happy! I have about 25-30 (each time I see new eggs, I throw them in the box so the population fluctuates). However, each day or so, I seem to be losing 1-2 and I can’t quite figure out why.

There is flow in the aquarium/in the box.

Maybe I am stressing them? Each day I take the box out and empty the content in a small container to clean it of excess food and others waste accumulated. I then syphon the baby in another container that I fill with food so they can eat (as the ziss breeding box has a mesh bottom, I am always afraid they aren’t getting food, even if I do put some on the edge). But I was wondering if doing so every day might be too stressful for them? It’s just that if I only syphon the breeding box, I feel as if it’s not clean enough and fear the rotting food left/forgotten might harm them?

Thank you!

Karen

[Fish Folk]

My suggestion is to just set it up like this -- a bunch of Java moss maybe with an added air line (perhaps the breeder box already has that) -- drop in 1/2 of a catappa leaf. Feed them, and leave them alone. Because it is a flow through, do not stress out about the stuff building up on the bottom. Add a couple of snails. They'll clean up, leave the babies alone with molm buildup on the bottom. The corydoras will be fine.

 

Edited May 24, 2022 by Fish Folk

[gardenman]

When fry die, it's usually due to insufficient food. Small fry need small food, but lots of it and in a flow through system keeping that small food where the fry are can be a challenge. As suggested, things like java moss that can trap some food for the fry and let them eat at will are handy. 

[Karen B.]

On 5/24/2022 at 1:41 PM, Fish Folk said:

My suggestion is to just set it up like this -- a bunch of Java moss maybe with an added air line (perhaps the breeder box already has that) -- drop in 1/2 of a catappa leaf. Feed them, and leave them alone. Because it is a flow through, do not stress out about the stuff building up on the bottom. Add a couple of snails. They'll clean up, leave the babies alone with molm buildup on the bottom. The corydoras will be fine.

 

Greetings!

I did what you told me, already had the catappa leaf in. Sadly I don’t have java moss at the moment (can’t find any, can you beleive it?!). I feed 2-3 times a day. I put floating plants on top.

I checked today (2 days later) and had 2 fry that were dead. I don’t understand 😓 Is it normal to lose some like that?

I also wonder - if you look at their bellies, it’s kinda red (looks redder in real life then on video). Is it the food (I give them hikary first bite and another powdered fry food I forgot the name. As well as frozen baby brine shrimp that I hatched few weeks ago) or are they injuring themselves on the mesh bottom of the breeding box?

 

 

Thank you!

[Fish Folk]

@Karen B. do you change the aquarium water much?

The metal grating… do they seem to stay on it or off it?

I assume the orange belly is from food eaten with carotenoids.

Very sorry for your losses. I’m not sure 🤔 

[Torrey]

@Karen B. in the first video especially, it looks like they are not comfortable on the wire mesh bottom. I don't think that is the cause of the belly being pink, as the reddest belly belongs to the largest belly... which tells me that the fry may not be getting equal access to food. Looks like some are eating more than others.

They may also be stressed by the bottom of the breeder box. I ran into that issue, and covered the bottom with plastic "aquarium gems" which gave the fry more smooth surface areas to rest on/clean without negatively impacting water quality. How much and how often are you feeding? How long does it take for the fry to eat all the food? Are there leftovers? What's the age difference between fry? And how frequently are you changing the water? How much water are you replacing?

Fry are far more sensitive to water parameters than their parents. Their gills are huge in proportion to the rest of their body, and if the water spikes ammonia after they eat, even for a short period, it will impact their health much faster than adult fish. I tend to keep a tiny sponge filter in with my fry, even if I cut a sponge prefilter down, and stick a plastic tube (for an uplift tube) and an airhose in with a small amount of air. It doesn't seem like much, but even that small extra amount made a difference in the health of my fry.

[Guppysnail]

@Karen B. I’m in a similar situation.  I just want to increase my population and see babies.  I have hatched them in 3 styles of breeder boxes with no success of them surviving past a week.  Last week I was vacuuming out the parent tank and sucked a teeny tiny baby up. Looked to be a week or so old.  I quickly pinched the hose so I could see what I just sucked up then released the fry back to the plant roots.  
The fry burrowed under the gravel pieces.  I have standard big box gravel.  I am now considering using my ziss box lined with gravel.  I’m wondering if they are that overtaxed by water flow, or possibly feeding on mulm and whatever it contains may help them survive?  This one was definitely a touch larger than the ones that I had in fry boxes. So I am hoping the gravel lining helps them survive.

I am not certain how helpful this info will be to you but I wanted to share. Hopefully we can find a collective knowledge base to help those of us struggling with corydora fry.  I know I have read a few threads of folks struggling.  A common theme I see in the struggling ones if bare breeder boxes and bare bottom tanks. The little guy I found was in among anubias roots. I was going to place some anubias with good roots and some java fern in the breeder. Thought that might give you some alternatives since you can’t find moss. 
Good luck. Keep us posted and share any secrets to success you find please. 

[gardenman]

I use the Fluval/Marina breeder boxes and keep them up constantly with some plants and snails in them. I don't really clean them other than siphoning out some snail droppings every month or two. Suffice to say the boxes are teeming with life. When I have fry that need safety, I put them in the established breeder box, and they thrive. The boxes may not look pretty as they have algae, gunk and whatnot in them, but if you're a baby fish, they're heaven. Massive amounts of food and no one trying to eat you. A pinch of food gets added to the boxes each day for the snails and whatever else is alive in the boxes.

I've never used a breeder box with wire mesh sides, but I've used breeder nets before and found that the fish in the tank predate the fry through the netting. Especially for bottom dwelling fish that lie on the bottom netting. I don't know if the fish in your tank could get to your fry through the metal mesh, but it might be possible.  

[Guppysnail]

On 5/27/2022 at 8:55 AM, gardenman said:

keep them up constantly

This is brilliant.  I have great luck with other if I have an ugly tank available.  I have the fluval breeder. I think I may set that up like this next get it running.