Why are my Celestial Pearl Danio fry dying soon after hatching?

[Allan B.]

Can the CARES community help me figure out why my CPD fry keep dying within 12 hours of hatching?

I've been trying to breed my CPDs, but for the last month or so all the wigglers that hatch have been dying within 12 hours of being born. I successfully bred and raised fry from this group of CPDs once in December-January, so I'm at a loss as to why my survival rate has been 0% this month.

Here's my setup—I've got a group of 12 CPDs (5 males, 7 females...not ideal, but I bought these a juveniles before they could be sexed) in a heavily planted 20 gallon long. When I want to breed them, I collect the eggs every day in a deli cup with java moss. I transfer the eggs into a .5 gallon Fluval hanging breeding box that's continually supplied water from a powerhead attached to a medium Aquarium Coop sponge filter. I also keep duckweed in the box with the fry, and put java moss in there once the eggs hatch. I also run an adjustable air stone into the box that's turned up enough to aerate the water but not cause too much of a current. I use a chunk of fine filter sponge (instead of the plastic gate that came in the box) on the box's outlet to keep the fry from escaping.

I test the water parameters in the breeder box and the main tank, and they match:

• Ammonia: 0 ppm
• Nitrites: 0 ppm
• Nitrates: 20 ppm (I use Easy Green)
• PH: 7.1
• KH: 5°
• GH: 6°
• TDS: 419 ppm
• Temp: 74-75°F
• I use a light amount of CO2, but not enough to turn the drop checker green.

Here's a picture of the breeding box:

Hopefully y'all can help...watching wigglers disappear is getting demoralizing.

 

EDITED:  Added water temperature.

Edited February 12, 2022 by Allan B.

[modified lung]

Try axing the air stone and powerhead and sponge. Connect your breeder box to the air and slow water intake to a fast drip.

[Harley Boraras]

That's a really nice looking tank. I'm interested to hear how you're progressing with this.

Do the CPD's leave any eggs in the densely planted parts of the tank and if so do any survive and grow to become adults?

[gardenman]

Dying within twelve hours is interesting. Most fry from egg layers have a yolk sac that provides food for them initially so food shouldn't be an issue in just twelve hours. It's usually two to four days after hatching before the fry get up and start to swim about at which point they need food. There are warnings that the fry lying on the bottom doesn't mean they're dead. Those warnings seem to imply that mistaking "normal" CPD fry from dead may be challenging. They are apparnetly fry that like to "play dead" for lack of a better phrase. You'll want to be sure that your dead fry are really, truly dead. 

[Allan B.]

On 2/21/2022 at 7:24 AM, gardenman said:

Dying within twelve hours is interesting. Most fry from egg layers have a yolk sac that provides food for them initially so food shouldn't be an issue in just twelve hours. It's usually two to four days after hatching before the fry get up and start to swim about at which point they need food. There are warnings that the fry lying on the bottom doesn't mean they're dead. Those warnings seem to imply that mistaking "normal" CPD fry from dead may be challenging. They are apparnetly fry that like to "play dead" for lack of a better phrase. You'll want to be sure that your dead fry are really, truly dead. 

Thanks for your response. These are definitely dead fry. I'm still trying to figure out what the issue is. I'm really hoping it isn't something environmental or genetic, because I'm also experiencing really low hatch rates now.

I'm going to try taking my healthiest male and putting him in a separate tank with a couple healthy females and try a control test.

[Beardedbillygoat1975]

I would put an indian almond leaf in and maybe some alder cones - they will provide tannins, humic acid and naturally antibacterial/fungal which may get them through. 

I think the other option would be use RO/distilled water with the eggs and see if that makes a difference. If I recall they prefer softer water but can tolerate harder water - they end up in isolated ponds with the changes in Lake Inle and the surrounding area so the ponds conditions can vary.