Cory sterbai eggs hatching

bavaria36 · Post by **bavaria36** » 02 Dec 2007, 21:33

My sterbais have spawned quite often and I am on my third attempt trying to raise the fry. I have been using the usual recommended method of removing the eggs and placing them in a small container floated in the main tank.

Something strange happens when I transfer the eggs from the main tank into the small container. The eggs would have been on the glass of the main tank for a few days. A few minutes after I have transferred the eggs, they start hatching. This has happened all three times now. It is as though the act of moving those eggs cause them to hatch within minutes.

However the fry seem to die after a couple of days. I was wondering whether I am damaging them while transferring the eggs.

Aaron

torbanite · Post by **torbanite** » 03 Dec 2007, 00:49

Hi Aaron,

I should preface my advice with "I am not an expert"

That said:

On transferring eggs when they are close to hatching:
I would suggest you try moving half your next batch early and the rest a bit later and note which half does better.
Maybe the eggs/embryos become more sensitive to environment changes, or the shells become thinner/more fragile the closer they are to hatching.

Other possible problems (these I can claim first hand experience of):
- What are you offering them as food & how much/how often? - once they absorb their yolk sac, they'll need food on tap.
- Localised overheating from the lighting.It gets quite hot under a closed hood with the lights on.
- If you inject CO2 for your plants. Replenishing the water in the tub from the main tank and aerating it with an airstone could cause rapid pH changes which the fry will not appreciate. If this applies to you, aerating the new water in a separate tub/jug for an hour or so before placing it in the fry tub may help (but is very time consuming). The lower your kH, the more dramatic this effect is likely to be.
- I found that adding _small_ doses of an anti fungal remedy prevented a lot of my lossages.

Anyway, I hope that helps.
Don't give up, tweak your method, one variable at a time if possible, and sooner or later you are bound to hit on a method that works for you.

Good luck!

bavaria36 · Post by **bavaria36** » 03 Dec 2007, 01:47

Thanks for the advice.

I have previously prepared BBS and added some to the container but I have never seen the fry actually eat any shrimp. Should I be adding it as soon as the fry hatch or a few days later ? Could I just crush some flake food very finely instead ?

I am floating the container in the main tank but I am leaving the light strip off to avoid direct heat on the container.

Aaron

apistomaster · Post by **apistomaster** » 03 Dec 2007, 16:01

I recommend removing the eggs soon after spawning is completed. They harden enough within an hour to be able to endure even handling by hand. One of my friends designed an ingenious little egg collecting device consisting of a single edge razor blade and small net to remove and capture eggs from glass surfaces.

They do not begin eating immediately after hatching so it might be best to wait 24 hours before beginning to feed them microworms. A small clup of Java Moss can help provide a few microorganisms for the early feeders to find until microworms are fed and it also aids in keeping the water fresh. Begin using very small amounts because these worms and associated media can quickly pollute the hatching container. After a few days try feeding very small amounts of freshly killed brine shrimp nauplii or decapsulated brine shrimp cysts. Then try live brine shrimp. If you refrigerate live nauplii then feed them, the nauplii will be lethargic and stay on the bottom where the fry feed. Eventually this isn't necessary because the fry will more actively hunt them down.

I have had some success using a black water additive to their spawning tank with regard to improving hatching rates even if I only use my tap water(pH 7.6, ~340 ppm TDS). Soft water with a ph below 7.0; pH of ~6.5 is better. Their fertility does improve with age so the first spawns may be disappointing but that will get better as the breeders mature.
Use water from the spawning tank, treat it with methylene blue, and start the eggs and fry in shallow, aerated containers with 4-inches/~10 cm of water.Remove the methylene blue after they hatch or even better, as soon as you can detect the developing embryos within the eggs, by way of the water changes but continue using the black water extract. Use an air stone operating slowly at first, then replace it with an aged sponge filter as you gradually increase the depth of the water in in the container. Add a few small snails to help clean up any uneaten food. Have matching water on hand to do daily water changes of the majority of the water since small containers are being used. This will help keep the water fresh and clean.
Some trial and error is inevitably required until you find what works best for you. Fortunately, Corydoras sterbai, spawn prolifically but this species is an egg eater so that is another reason for removing the eggs or breeders soon after spawning.

bavaria36 · Post by **bavaria36** » 03 Dec 2007, 20:53

Thks Larry,

will follow your advice. I have removed all the eggs I could from this spawn using a blade ( although I did lose quite a few that did not sticK to the blade.).

they are now in a small hatching container and as soon as they hatch I am moving the fry to another container that is floating in the main tank. Until now I have around 25 fry and only one has died.

It has been a little over 24hrs since the first egg hatched so I have now crushed some Tetra colour bits very very finely and added that to the container. Do you think that this will work until the BBS hatch ( hopefully by tomorrow ) ?

Should I be able to see the fry actively eat ? They are moving around but I have not really seen them actually take any food.

I was also thinking of transferring the fry to one of those blackworm keepers ( the ones with netting at the bottom ) and floating that in the main tank. This should make it far easier to keep the water clean.

Thks for all the suggestions

Aaron

apistomaster · Post by **apistomaster** » 04 Dec 2007, 01:48

I like your idea of using the worm keeper floating in your tank. Tetra Color Bits crushed will be a good food. Just feed your fry very little and frequently.
I would crush to a powder consistency and mix it with a little water in an old prescription bottle. Shake well before using then feed the suspension by the drop from an eye dropper. Refrigerate this suspension. It should store well for several days.

Corydoras larvae are not as active as they are after completing their metamorphosis but they should move around some.
I would add a few small plants and some thing they can hide under. Another form of shelter that works very well are those hollow ceramic biomedia. A few dozen of these in their container(the worm keeper) will provide them plenty of small caves that they will use. Most Corydoras species' fry I have raised are very reclusive. It is their instinct to find shelter from potential predators.

bavaria36 · Post by **bavaria36** » 04 Dec 2007, 20:10

Larry,

the fry are three days old now and I can see that they have lost their yolk sacs. I have not lost any yet and there are still around 15 eggs in the hatch container that also look viable.

I added a few cutting from the end of some flower stalks that were in the house thinking that this could serve as a potential starter food if there was some infusoria in the water that the flowers had been sitting in. I did not see them eat and have since changed the water a few times but the stalks have become their shelter. All the fry hide underneath them as you had noted in your post.

I now have plenty of BBS and today added some after filtering the shrimp through a coffee filter. Should i see the fry chasing the BBS around the container ? If not does this mean that I have added the BBS too early ?

Aaron

apistomaster · Post by **apistomaster** » 05 Dec 2007, 00:56

The larvae at this stage do not pursue their food very much. They just grub around and pick up whatever they detect that smells right. Or if a live nauplii or odd Rotifer bumps a whisker they will reflexively suck it up. As larvae they tend to be tiny ambush predators; at least that is my impression.
Once the fry complete their metamorphosis into the typical Corydoras body plan, their visual acuity is much improved and they will actively hunt the brine shrimp nauplii by both sight and sensation.

bavaria36 · Post by **bavaria36** » 05 Dec 2007, 01:31

Thks for the info Larry,

I guess I just need to be patient. I am sure that most of them have absorbed their yolk sacs now as their shape has changed. I'll keep the BBS ready and keep an eye on them.

Aaron

bavaria36 · Post by **bavaria36** » 06 Dec 2007, 04:17

All the fry are still alive and some of the eggs that I collected 4 days ago now are still hatching so the group is still growing.

Tonight for the first time I confirmed that they have eaten. Even though I never actually saw them feed I noticed that their bellies were all orange. I have been adding live BBS and some finely crushed Tetra Bits to the container. Both happen to be orange so I am not quite sure what the fry have actually eaten.

I am taking daily photos of the progress of this spawn and posting them here.

http://www.pbase.com/bluefin/corydoras_sterbai

Aaron

bavaria36 · Post by **bavaria36** » 07 Dec 2007, 03:10

Day 5 and all the fry are still alive, free swimming and eating. All the remaining eggs that I had in the second container hatched last night too.

And to cap it all the adults have spawned again in the main tank !!!

Aaron

bavaria36 · Post by **bavaria36** » 09 Dec 2007, 22:23

It's been 8 days are the fry are doing very well. I have only lost two out of around thirty and I think that I killed those myself accidentally during a WC.

As Larry had pointed out, now that they have completed their metamorphosis from the larval stage , they are far more active. Their bellies are always full. I am still feeding BBS and crushed Tetra bits. They seem to like both

Aaron

sskruzr · Post by **sskruzr** » 10 Dec 2007, 18:57

What size and age did your Sterbai start spawning? What size tank do you have your breeders in? What are you feeding them? I've 17 Sterbae and am interested in getting them spawning. Thanks

darkwolf29a · Post by **darkwolf29a** » 10 Dec 2007, 19:56

Congrats on the fry.

Keep the pictures coming.

I too am interested in the methodology of spawning them.

apistomaster · Post by **apistomaster** » 10 Dec 2007, 20:25

I have had Corydoras sterbai begin spawning at nine months post-hatch. These were specimens that received routine care and feeding. I think they could be bred a little sooner if they were pampered with more live worms in their diet and given large frequent water changes.

bavaria36 · Post by **bavaria36** » 11 Dec 2007, 00:55

The Sterbai have been at me for almost exactly one year. I must point out though that I bought them as adults ( they were wild caught )and in very good shape already when I got them.

I have kept them in a 120 gallon planted tank with 8 discus for about 10 months and they were very , very well fed ( BH, FBW, BBW, tetra bits, BH mix , shrimp etc etc ). I moved the discus to their own tank a couple of months ago and they sterbai spawned just a week later.They may have been spawning earlier but I do not recall ever seeing any eggs.

I lost all the first spawn after two days so this time when they spawned I collected the eggs carefully and just followed the advice I got on this post and a few others.

Photos from Day 9

http://www.pbase.com/bluefin/image/90171853

Aaron

bavaria36 · Post by **bavaria36** » 13 Dec 2007, 02:11

Yesterday I had my first losses ..... came back late from work and found the five biggest fry dead. I was gutted cos these were the best ones. I could clearly see that their bellies were full of food so that was not the problem. I suspect that the water could have got fouled as I had added BBS in the morning and they had been sitting in the bowl all day. Maybe the oxygen content dropped during the day and this killed the largest fish ??

Today I had two more die but this time they were medium sized ones. It's strange because I had changed the water several times and was being very careful with food. The water was very clean when I found them. Is it time to move the fry to a 10 gallon tank with its own filter now ?

Aaron

apistomaster · Post by **apistomaster** » 13 Dec 2007, 20:19

You are at a stage where most losses of Corydoras fry occur. I really don't know why they are so susceptible at this stage but it is problematic with most of the Corys except C. aeneus and C. paleatus, at least for me.

bavaria36 · Post by **bavaria36** » 14 Dec 2007, 02:55

Larry,

I can only guess that I might have missed a WC or
left those BBS too long. I found one more dead fry this morning but no more this evening.

I am upping the WC's now so while I am in the house I change the water every few hours.

When would you recommend that I can move them from the plastic bowl into a 10 gallon tank with a mature filter ? I have one ready to go.

Aaron

bavaria36 · Post by **bavaria36** » 15 Dec 2007, 03:04

Today something strange happened. I got home from work and checked on the fry. All were still alive and doing well. The water was clean and they had eaten the crushed flake food I had out in earlier today. After I changed the water I prepared some BBS and added it to the dish.

Twenty minutes later 10 of the fry were dead including all the large ones. All their bellies were really full of shrimp. Could they just have gorged themselves so much that it killed them ????

Aaron

bavaria36 · Post by **bavaria36** » 19 Dec 2007, 17:50

Since I lost those fry I transferred them from the plastic dish floating in the main tank to one which has a netted bottom. This enables the water to be kept much cleaner as it is constantly being mixed with the main tank water. Since then I have only lost one more fry so it seems to have worked.

Aaron

apistomaster · Post by **apistomaster** » 19 Dec 2007, 20:24

Losses tend to be high until they resemble their parents.
Keeping their water as clean as possible is what works for me. Even so, only about 40% survival is the best I've done. I had to raise many spawns to end up with the 500 I sold last year.

bavaria36 · Post by **bavaria36** » 20 Dec 2007, 04:12

At what age/size could I let them loose in the main tank ? I ask because I will be travelling out of the country over the Christmas period and have no one who could really take care of them and feed them a couple of times a day in the container.

The fry are between two and three weeks old now and they feed very well in the container. Do they stand any chance of surviving in the main tank if I release them ?I was hoping that they would have a better chance of feeding themselves in the 120 gallon planted tank ...

Aaron

apistomaster · Post by **apistomaster** » 20 Dec 2007, 14:55

Whether they would be safe in your main tank would depend on what is in it. If its just the adult C. sterbai, then its probably fine.

I would consider adding the hollow ceramic bio-media I've mentioned before to provide the fry with microhabitats.

bavaria36 · Post by **bavaria36** » 20 Dec 2007, 18:08

Yes,Larry

since I removed the discus the 120 gallon planted tank only has 8 adult Sterbai in it. I am pretty sure that they would not touch the 3 week old fry. There is also plenty of cover in the tank ( plants, wood etc ) so they should find plenty of shelter.

I was wondering about whether they would find enough to eat though. I will have someone come in every two or three days to feed the fish.

Aaron

Carp37 · Post by **Carp37** » 21 Dec 2007, 11:49

Hi Aaron-
regarding the losses of fry just after adding baby brine shrimp, I was just wondering how thoroughly the brine shrimp were rinsed prior to adding them. The only reason I ask this is that some corys are especially sensitive to salt in the water, especially as juveniles, and I would have expected live brine shrimp to foul water up much less than prepared foods such as crushed flake etc.

bavaria36 · Post by **bavaria36** » 21 Dec 2007, 14:50

Carp37 wrote:Hi Aaron-
regarding the losses of fry just after adding baby brine shrimp, I was just wondering how thoroughly the brine shrimp were rinsed prior to adding them. The only reason I ask this is that some corys are especially sensitive to salt in the water, especially as juveniles, and I would have expected live brine shrimp to foul water up much less than prepared foods such as crushed flake etc.

Actually I did not rinse them. I filtered the shrimp through a coffee filter and then shook the filter paper around in the bowl with the fry.... Could that have added enough salt to kill the fry ?

Aaron

apistomaster · Post by **apistomaster** » 21 Dec 2007, 18:08

You should always rinse the bbs with fresh water before feeding them to your fish. Bbs do spoil much faster than prepared foods and can contribute to high bacteria counts. Even so, Corydoras tolerate salt as well as any other SA fish. I don't recommend salt but I have used up to one tsp/gal with C. sterbai for a week in the process of treating them for disease with no ill effects. The sensitivity to salt of Corydoras is one of those old myths that has no basis in fact.

The fry should be fine while you are away.

Cory sterbai eggs hatching

Cory sterbai eggs hatching

Corydoras Sterbai spawn

Sterbai fry