Why do my corydoras aeneus fry die?

kruit

So I've tried raising corydoras fry 3 times now, all three times significant death of the fry after ca. 8 weeks.

Observations:
Attempt 1:
ca. 40L tank, cycled and established with heater and filter, planted
ca. 30 corydora fry and 6 cloud minnow fry (all about the same age)
20% water change once every 2 weeks
unsure about ammonium, nitrite and nitrate concentrations
pH 7.5
The fry were growing nicely, but after ca. 8 weeks one after the other corydoras died, cloud minnows were not affected at all
Symptoms: 'hooked' tail, not able to swim properly, lying on their side
I put the survivors in the (200L) community tank, and they are ok (ca. 6 months old now)

Attempt 2:
100L tank, cycled and established, heater, filter, planted
ca 30 fry
20% water change once or twice per week
ammonium: <0.05 (JBL test kit, lowest on the scale is '<0.05')
nitrite: < 0.025
nitrate: 1
pH 7.5
again the fry were growing nicely, but after ca 8 weeks same symptoms
relocated 15 survivors to a 40L tank, doing 20% daily water change. 10 of these survived, ca. 4 months old now

Attempt 3:
10L tank, no heater, but room temp. ca. 25degC, airstone, bare bottom, 1 small plant
9 fry
50 - 75% water change daily
parameters just before water change:
ammonium: <0.05
nitrite: < 0.025
nitrate: 1
pH 7.5
they are circa 8 weeks old now, and one of the fry shows symptoms similar to the previous attempts for the last 3 days
75 - 90% daily water change for the last 3 days shows no improvement


In all 3 attempts the parents are from the same group of 10 corydoras, unsure of age but I believe somewhere between 5 and 8 yrs old, presumably siblings

As for the pictures:
the first picture (4monthsold) shows 4 of the fry from attempt 2. The bottom right one clearly shows a deformation
the second picture (2months, deformed) shows the one from attempt 3 with a slight deformation. Picture taken 3 days ago
the third picture (2months_healthy) shows one from attempt 3 which is healthy
the fourth picture (2months_deformed2) shows again the deformed one, but picture taken today, lying on its side

My thoughts:
water change (or relocating to another tank) seems to have a positive effect, but attempt 3 indicates that there is something else wrong as well
also: no measurable levels of ammonium or nitrite and the cloud minnows in the first attempt were not affected at all
all 3 attempts the symptoms appeared when the fry were ca 8 weeks old. Coincidence?




Anyone here with ideas on what can be wrong?
 

Attachments

  • 4monthsold.jpg
    4monthsold.jpg
    136.5 KB · Views: 18
  • 2months,deformed.jpg
    2months,deformed.jpg
    159 KB · Views: 17
  • 2months_healthy.jpg
    2months_healthy.jpg
    138.2 KB · Views: 18
  • 2months_deformed2.jpg
    2months_deformed2.jpg
    185 KB · Views: 18

MacZ

Hmmm... I would presume either genetics or a nutrient deficiency. What do you feed them how often?
 
Upvote 0

kruit

Hmmm... I would presume either genetics or a nutrient deficiency. What do you feed them how often?

Thanks for your feedback.


For feeding:
attempt 1: a combination of flakes and tetra tabimin (tablets), daily
attempt 2: tetra tabimin tablets, one tablet once or twice daily. presumably they were able to scavenge food f rom between the plants as well
attempt 3: tetra tabimin tablet, 2 times 1/2 tablet per day, occasionally spirulina


It could be a genetic defect, verifying this theory will be a bit time consuming though.
 
Upvote 0

MacZ

Yeah, there's your problem already.
Tetra dry foods contain vitamins and minerals, but when it comes to the ratio of proteins to fat to fiber they are rubbish. Also much too much cheap fillers like grains and fish meal.

Try live freshly hatched artemia (aka baby brine shrimp), frozen cyclops, microworms, young tubifex... they need foods for carnivores, so scratch the spirulina. Catfish doesn't mean herbivore as many tablets make people think, printing a cory on the package and saying "60% vegetables". That's bound to give fry deficiencies. For vitamins and minerals use vitamin drops by any manufacturer, they are all ok as there is not much you can do wrong when mixing them in frozen food.

It could be a genetic defect, verifying this theory will be a bit time consuming though.
Actually no. If it still shows up with the correct feeding it's genetics. If not, not.
 
Upvote 0

kruit

Many thanks for the good advice!

Although I hadn't considered nutrient deficiency, what you write makes sense, and I see how that can explain the symptoms I've seen.

I will follow your advice, feed them (live) artemia, and give them more varied food.
I also didn't realise corydoras were carnivores; I thought they were omnivores. As you said I'll scratch the spirulina.
 
Upvote 0

richiep

I transfer eggs into 8"×4"×6" and are kept there for 2 to 3 months feeding brine shrimp daily and occasional powdered flakes, although the breeder as its own water supply from the main tank I still change out about 50% daily,I do get the occasional deformity but I believe the small space means they get food , in larger tanks this can be a problem not finding food
My last hatch of 80 I lost 3
I have had as many as 120 in this breeder and as long as they get brine shrimp and regular water changes I don't have problems
The picture shows the size before I put them into a 4gal tank to grow out for a few more months
Hope this helps
 

Attachments

  • 20200822_163041.jpg
    20200822_163041.jpg
    125.6 KB · Views: 18
Upvote 0

kruit

I transfer eggs into 8"×4"×6" and are kept there for 2 to 3 months feeding brine shrimp daily and occasional powdered flakes, although the breeder as its own water supply from the main tank I still change out about 50% daily,I do get the occasional deformity but I believe the small space means they get food , in larger tanks this can be a problem not finding food
My last hatch of 80 I lost 3
I have had as many as 120 in this breeder and as long as they get brine shrimp and regular water changes I don't have problems
The picture shows the size before I put them into a 4gal tank to grow out for a few more months
Hope this helps

It definitely helps; it confirms MacZ's theory about nutrient deficiency
 
Upvote 0

richiep

Its MacZ post that led me to add this
 
Upvote 0

Yeoy

It's been touched on but definitely recommend sticking to a strong water change regimen, especially while the fry are young. Especially if you're feeding them often, 30 fry can produce a lot of waste in a small space. You obviously want to keep the water parameters stable but changing the water every second day would be OK.

It's also wildly accepted that a lot of fry produce a chemical/hormone that slows down the growth of other fry in the tank. So if you have 30 fry producing this, regular water changes help a lot.

Hopefully it all pays off and you'll be posting pics of huge cory batches soon!
 
Upvote 0

Similar Aquarium Threads

  • Question
Replies
3
Views
172
PurpleReign19
Replies
3
Views
165
Noroomforshoe
Replies
5
Views
145
jdhef
  • Question
  • mygerbilprince
  • Platy
Replies
3
Views
122
mygerbilprince
  • Question
Replies
2
Views
184
Thiefbird

Random Great Thread

New Fish Breeding Threads

Top Bottom