Problem With C.habrosus Fry

[mikev]

Hi,

I need some expert help to try to pinpoint a problem....

I'm repeatedly losing C.Habrosus fry and cannot see what is wrong. The most puzzling deaths occur at about 10-14 days after hatching.

So far there were five attempts (they provide eggs regularly), with the following outcomes:

Hatch 1: 6 fries out 10 eggs, all suddenly die at 2 week mark.
Hatch 2,3: many bad eggs, little fry dies at the time of hatching (likely contamination from bad eggs, this problem solved)
Hatch 4: 11 out 15 eggs, 2 deaths in the first two days, 4 died since yesterday night. (After each death, full container and water change, trying to save the rest, this worked after first two losses, did not help yesterday).
Hatch 5: so far 17 out of 22 eggs,.... these I'd like to try to save.

Feeding: filter squeeze+microworms for three days after yolk sac has been consumed, then switch to artemia. At the time of death, fish has been active and eating artemia for several days.
Water changes 30%-50% daily.
Container: Plastic, footprint slightly larger than that of a 2.5g, 1"-2" water depth. Bare bottom. Airline, but no filter.

I simply cannot see what can be wrong .. perhaps someone else has an idea?

Incidentally, I use exactly the same technique with C.Panda, without a problem -- some fry may die soon after hatching, but once they start eating artemia, they are stable.

Thanks!

 

[mikev]

Append:
Just in case:
TDS around 150, pH around 7.1, R/O water, temp around 77F (room heated); an effort made to keep the container as clean/sterile as possible; there are no diseases anywhere in the fishroom right now that can explain the losses (and everything is separate anyway).

 

[Harlequins]

Sorry to hear some fry arent making it.

I'm a newbie to cory fry raising so not much help really,but one thing i have noticed the past few days from my 8 c.trilineatus fry (2 from the first hatch,6 from 2nd hatch,3 eggs on 3rd spawn didnt hatch,my fault,1 from 4th hatch,theres another egg due any day,and 2 i've just found from today )is that the nitrite is present,i now i have to do 2 x 50% w/c daily has the sponge filter isnt working fast enough to clear their bio load.

I only find a few eggs each time,has the platies likes them too

At the moment i have ungraded to a 24l tank with a little sand,airstone,heater and sponge filter,i was doing 50% w/c daily and feeding them on first bites soaked in tank water and baby brine shrimp then feeding them using a pipette straight by them in the tank.
It appears to be working so far (touch wood) and they are now 3 weeks old,with a new 2 day old fry in a tub floating on top.

I was wondering if a filter might help?

Hopefully someone can help more

 

[Inchworm]

Hi mikev

While I haven't raised any C.Habrosus myself, I have raised other species of corys and noticed that, in general, some methods seem to work better than others. I used to use bare bottom fry tanks but gave that up because of the bacteria that breed at the bottom. It's actually easier, and I have better results, using a thin layer of sand.

Not counting a few that might naturally die off from poor development, most of the later losses are usually from bacterial infection. Using a sand bottom, which should be stirred regularly, might give them an opportunity to develop natural immunity to some of these. I would also question your use of RO water for the same reason. Their natural habitat is anything but sterile.

Are you feeding them newly hatched brine shrimp or decapsulated brine shrimp eggs? I've heard that the eggs spoil rapidly, but with a sand bottom and big water changes I haven't had a problem that I could pin on them yet. I used to use microworms but have switched to Hikari First Bites and that seems to be working well too.

Please let me know if any of these suggestions help.

BTW, while C. pandas were hard for me to get established, they breed well and I find their fry are surprisingly easy to raise. Since they spawn in small batches, I just add them to the tank with whatever else I might be raising at the moment.

 

[mikev]

Hi Inchworm,

C.Habrosus seem different. I can only compare with C.Panda and C.Metae myself (I'm not into cories much), but a friend used the same techniques with other species successfully.
One obvious difference is smaller fry size; I'm not even sure they can take Hikari First Bites the first day..... (and I'm not crazy about Hikari.... bad results with other types of fry). GP's, perhaps?

I don't think the losses are due to poor development -- they grow rapidly until the moment they die

I'm using bare bottom plastic specifically to be able to keep the tank clean... I can swap containers easier than if they were filled with sand.

The results, however, do not seem to depend on sterility: the first group got some java moss from from the parents tank, the later groups an environment as clean as possible.... no difference.

The food was new hatched artemia. I gave decap to the first group of fry the day before they died....not sure if there is a connection, but no more decap for them. (C.Panda in another container got the same decap and did not mind it any).


To add to the mystery: a friend of mine with more then a hundred species breeding record, tried breeding C.Habrosus a year ago.
Soft tap water/microworms/no attempt to maintain sterility/fish unrelated to mine --> same results as I get.



Yes, C.Panda's are easy.... I don't get too many of them (probably the tankmates are at fault), so I simply put new fry with older ones and they survive just fine.

 

[mikev]

Harlequins,

Thanks.

Nitrites are not a problem. Despite its small size, I actually have a cycle going in the container.... I don't see how a filter would help.

 

[Inchworm]

Hi mikev

You could be right about it being a problem specific to the dwarf species. Maybe Coryologist will see your thread and comment. I believe he's raised a few of them.

Here's a hint about the pandas. They are often egg eaters and will also hide their eggs. I hang metal thermometers in their tank and they spawn on the side facing the glass. They can then easily be lifted out and moved to another container to hatch.

 

[mikev]

Thank you, Inchworm, hopefully he can shed some light on this.

Actually, I wonder: the remaining 5 fries are about 8mm long now.... think I can try to give them fine grain catfish pellets? (Sera or Tetramin).
Live artemia is not exactly the natural food for them, even if Pandas seem to do fine on it.

Habrosus, incidentally, are egg eaters.. at least mine are. I can find lots of eggs because they are regular: W/C on Monday, eggs on Tuesday, eggs are gone on Wednesday. Single species tank, gotta be them...

-----

On Pandas: impressive. More eggs than I ever saw from them...I get very few, all well hidden in the plants. I think Neocaridina is at fault, they bred to huge numbers.. plus the tank has loaches in it.... I'm not looking for more fry from them, there are too many already and no challenge in breeding them...so I only take the eggs that I happen to see.

 

[Coryologist]

Greetings. I have never kept C. habrosus, until a few months ago. I spawned them for the first time on September 12th. They were my 60th species. They have done no better or worse than any other Cory I have spawned. I went to pull eggs from the moss a few days ago as they are spawning continuously and found around 50 fry under the moss in a tank with about 40 adults.

I have stopped pulling the eggs and I am just letting them hatch in the tank with the adults, under a big thick wad of moss.

There are so many different things that could be causing your fry deaths that even offering suggestions is nothing more than an exercise in futility. Experimentation is your only hope of getting better results. One thing I will say. I have never used a drop of RO in my life. - Frank

 

[mikev]

Thanks, Frank,

OK, it is good to know you have no problems with them... so either my stock is bad or I'm doing something wrong.

A couple more questions to avoid unneeded experimentation (which would kill more fry )

1. Do you happen to know anything about C.Habrosus salt tolerance? (I know for a fact that C.Panda has very high tolerance...if this not true for C.habrosus or for cories in general, this would explain)

2. Can a fry that is about 2 week/8mm already be brought up on dry food alone? (choices: smallest GP's/crashed flake/Sera tablets); if yes, which is the best?

I need to test this a bit better, but the current suspicion is that the small amount of salt coming from artemia feedings may be the problem....

 

[Tolak]

A couple things I've learned from some local cory breeders; snails or half the usual dosage of copper sulfate pentahydrate. A few snails in the tank once the fry are swimming keep the bacterial film at the bottom of a bare tank to a minimum. A common problem around here is velvet, and it seems to affect the gills of small fry. You don't have the usual visual of a goldish sheen or sprinkling as the fry are so small. The copper keeps this at bay.

You can't use both at once; copper kills inverts. Be aware that levels of copper in softer water are not stable, and copper should be used in a clean tank only, as it will concentrate in algae, kill it, and be rereleased into the water column.

 

[mikev]

Thanks, Tolak,

Yep, snails probably would be a good idea now. (I use them with other fry...better snail poop than rotting food). I'll put a few small ones in tomorrow.

Copper is not for me --- I'm using R/O mostly because there is enough copper in tap to kill some fish, I'll never add it myself for any reason.
(And you are right -- when I switched to R/O I still had copper being slowly released from the substrate -- I had to replace gravel in tanks with most sensitive fish just to get rid of it.)

 

[Coryologist]

Thanks, Frank, OK, it is good to know you have no problems with them... so either my stock is bad or I'm doing something wrong.

If you're getting fry, the chances that there is something wrong with your breeding stock is slim.

A couple more questions to avoid unneeded experimentation (which would kill more fry )

1. Do you happen to know anything about C.Habrosus salt tolerance? (I know for a fact that C. Panda has very high tolerance...if this not true for C.habrosus or for cories in general, this would explain).

Corys are not to have a high tolerance for salt. Just because you add salt that would be considered a high level and your C. panda don't die, proves nothing. You have no idea what physiological damage is taking place, short of killing the fish.

2. Can a fry that is about 2 week/8mm already be brought up on dry food alone? (choices: smallest GP's/crashed flake/Sera tablets); if yes, which is the best?

Anything is possible. The question should be, is it optimal? I would certainly never try to raise fry that way - but - as they say - your mileage may vary.

I need to test this a bit better, but the current suspicion is that the small amount of salt coming from artemia feedings may be the problem....

At those levels that is extremely unlikely. I thought you were talking about using salt as a prophylactic. Suggest you look elsewhere for your problem. I consider artemia nauplii a very poor food choice for Cory fry. It starts to rot the minute it dies and it is usually overfed. I use decapped brine shrimp eggs and that one particular food has become the diet staple in my fish room, regardless of specie or age. It is much higher in nutritional value, is less expensive and it is easier to gauge how much you are feeding.

Additionally, a thin layer of sand on the bottom is highly recommended to deter the growth of harmful bacteria, the leading cause of fry death. - Frank

 

[Tolak]

Something Frank mentioned, and a light bulb went off; bbs hatching. Make sure all the equipment used for hatching is clean, change hatchery water after each batch & clean the container. I've heard of people having bacterial problems from less than clean bbs hatcheries & procedures.

One trick I learned some time back is to add a few drops of chlorine bleach to the hatchery when setting up. This gasses off in 24 hours or less, no different from chlorine, and adds another level of disinfectant to the hatching process. I use straight tap, no dechlorinator in my bbs hatchery. I can smell the bleach when I first set it up, in 24 hours there is no bleach smell.

 

[Inchworm]

1. Do you happen to know anything about C.Habrosus salt tolerance? (I know for a fact that C.Panda has very high tolerance...if this not true for C.habrosus or for cories in general, this would explain)

Corys do not have a high tolerance for salt since it isn't in their natural habitat. It's OK for medicinal purposes but I could see where it might be a problem with fry.

2. Can a fry that is about 2 week/8mm already be brought up on dry food alone? (choices: smallest GP's/crashed flake/Sera tablets); if yes, which is the best?

I have a batch of 10 day old C. aeneus (albino) fry that have been fed only Hikari First Bites and decapsulated brine shrimp eggs, and some C. pandas and C. venezuelanus that are older and were switched to that diet a few weeks ago. They all look very good and are plumper than I would have expected with microworms. Once the little ones get big enough I will add finely chopped blackworms and shaved frozen bloodworms to their diet. I haven't used the other products you mentioned, but if you can get them fine enough they should work. The Hikari First Bites is like a powder.