Help with small corydora's

[sannick]

Hi all,

We have 2 tanks, 1 About 400l ( 100 gallons ) and one about 20l ( 4 gallons ).

In the big tank there are 10 corydora paleatus with the parameters of NO3 : 10mg/l NO2 : 0mg/l GH: 8 KH: 7 PH:7.2 at 23C are 73,4F.

After a water change the cory's started breeding so we took out 8 eggs en raised the fine no problems at all.
Now the second time of breeding we took out about 40 eggs bus some where empty and never hatched ( I think about 35 did ). So we started a small second tank and did a fish in cycle so we changed 25l of water every day 5l at the once and everything went perfect. And about 4 to 5 weeks in the aquarium was cycled so we stared to change less and less water till about 2 times/week 5l.

Now about 2 months of having them in the tank they start dying. Yesterday it was 3 and today there where 2 and there will be more because some are so skinny and don't want to eat.

The small tank has the same water parameters as the big tank. The only difference is the temp. this is only 20C are 68F.
The ammonia is 0 and for food they get 2 times a day half a spirulina are krill tablet and they get some frozen bloodworms are some sera vipagran. ( So 3 times per day food)

However there are 3 who are bigger and nice and chubby they are about 1cm ( 0.4 inch ) bigger.

Can someone please help me are point out what i'm doing wrong here.

 

[DoubleDutch]

What is the substrate like ? Same as in the main tank ?

 

[ghyti]

Sounds like they are not eating. I don't know what sera vipagran is and I suspect that frozen blood worms are too big for them to eat. Try some micro-worms if you can get them, or possibly newly hatched baby brine shrimp.. When they get a little bigger, shrimp pellets or Repashy gel food works great.

 

[sannick]

The substrate is the same white sand as in the main tank.
The vipagran is a small pallet food and the blood worms they can eat only the big ones are to big.

But i'l try some mirco-worms

 

[Byron]

I can't explain the dying, but I can offer a suggestion on food to improve things which may help in the future. Put some dried leaves in the fry tank; these will decompose and as they do they produce a lot of infusoria, which is the first food of almost all fry, and it has been shown that fry grow faster and seem healthier when they have infusoria. I use dead oak leaves collected from my back garden in the autumn, but leaves of most hardwood trees work, maple, beech, etc. Or you can buy almond leaves in some fish stores.

Go easy on the worms; this is not a particularly healthy food. I would not feed bloodworms at all to fry. Insects, insect larvae, and crustaceans are the primary natural foods of Corydoras. Once they are past the initial infusoria stage, the micro Bug Bites would be a good food, and shrimp pellets (Omega One is a better brand for these).

 

[sannick]

First of all thanks for the reactions but i think there is something else going on.
About 5 mins ago 1 was floating a bit upside down than it went to the surface and than it was trying to get down again but not just swimming but spiraling down like a paper airplane would. So i'm starting to think parasite that is killing them 1 by one. I also noticed some of them have there tails really clamped.

So i'm putting them all in a bucked with some meds so they have 100% clean water and i will threat the tank as well and in a week i will do a 100% water change in the tank before they go back if there are some alive by than.

 

[DoubleDutch]

I can't explain the dying, but I can offer a suggestion on food to improve things which may help in the future. Put some dried leaves in the fry tank; these will decompose and as they do they produce a lot of infusoria, which is the first food of almost all fry, and it has been shown that fry grow faster and seem healthier when they have infusoria. I use dead oak leaves collected from my back garden in the autumn, but leaves of most hardwood trees work, maple, beech, etc. Or you can buy almond leaves in some fish stores.

Go easy on the worms; this is not a particularly healthy food. I would not feed bloodworms at all to fry. Insects, insect larvae, and crustaceans are the primary natural foods of Corydoras. Once they are past the initial infusoria stage, the micro Bug Bites would be a good food, and shrimp pellets (Omega One is a better brand for these).

I recall an advise not to feed bloodworms to Coryfry.

 

[AdoraBelle Dearheart]

First of all thanks for the reactions but i think there is something else going on.
About 5 mins ago 1 was floating a bit upside down than it went to the surface and than it was trying to get down again but not just swimming but spiraling down like a paper airplane would. So i'm starting to think parasite that is killing them 1 by one. I also noticed some of them have there tails really clamped.

So i'm putting them all in a bucked with some meds so they have 100% clean water and i will threat the tank as well and in a week i will do a 100% water change in the tank before they go back if there are some alive by than.

I believe there are some bacterial infections that can kill cory fry, and sounds a bit like this. @Colin_T may know more.

Question that is relevant to the above, I promise. You said the sand was the same white sand as the parent tank - did you take it FROM the parent tank? Or just same brand/from the same bag, and unused until now?

 

[sannick]

At the moment they are all in a bucket with omnipur ( meds ) just to be safe.
Adorabelle dearheart,
I think so to parasite are bacterial infections. To many to fast for something else i think.

The sand was brand new. The bag was open but wasn't used before.

 

[AdoraBelle Dearheart]

The sand was brand new. The bag was open but wasn't used before.

That's actually what I was worried about. It needs to be sand from the parent tank, sand that's aged, since there are good bacteria as well as bad. I don't entirely know why, but it's what I was told by someone who really knew her stuff, and I believe that's what's happening here.
Sounds as though you've also been feeding a lot of larger solid foods, have you been cleaning the substrate while doing water changes? Easiest way with baby cories is using a turkey baster to blast and suck up the debris.

I worry about adding all these chemicals and moving them into a bucket. In your shoes, I would give the substrate in their tank a thorough clean, then add a good amount of sand taken from the parent tank. Do a large water change, using a mix of water from the parent tank, and fresh clean (declorinated) water, temp matched to the nursery tank before adding it.

Urgently get fry food for them. I feed my bronze and pygmy fry microworms. baby brine shrimp, and add a lot of things like Indian almond leaves and moss for infusoria. This time with the batch of bronze cory fry I have now, I've added some cherry shrimp to help clean up any uneaten food, but the fry are also in a net breeder box in the parent tank, so most uneaten food passes through the netting.

 

[coriesinhawaii]

First of all thanks for the reactions but i think there is something else going on.
About 5 mins ago 1 was floating a bit upside down than it went to the surface and than it was trying to get down again but not just swimming but spiraling down like a paper airplane would. So i'm starting to think parasite that is killing them 1 by one. I also noticed some of them have there tails really clamped.

So i'm putting them all in a bucked with some meds so they have 100% clean water and i will threat the tank as well and in a week i will do a 100% water change in the tank before they go back if there are some alive by than.

If you decide to treat with medications I suggest only treating the affected fish in a separate quarantine tank. Putting the meds into the main tank could damage your biological filter.

If it is actually an infection it seems like it would have to be an opportunistic one since you haven’t added in any new fish or plants recently. So it would have to be an organism that is present in the tank all the time and normally doesn’t cause problems unless the fish are very stressed (perhaps from the recent fish-in cycling?) So if that’s the case it wouldn’t be necessary to eradicate the organisms from the tank anyway. Just give the affected fish the boost they need to fight it off.

 

[coriesinhawaii]

Make sure you pick an an antibiotic that treats internal infections. Kanamycin would be first choice for fish that are not eating. Otherwise use another antibiotic that is labeled for treating septicemia.

Only use 75% of the labeled dose for cories because they are sensitive to medications.