Cory fry not eating and dying

[Emma_M]

Hi everyone,

I have had a few batches of eggs from my Julii cories. They have only laid a few at a time and the other fish have been getting to them, but I've had about 3 batches hatch 2-5 fry. I cannot get the fry to eat and each time they have died. I have tried fry food from Aquarium Coop (https/www.aquariumcoop.com/produc...p.com/products/aquarium-co-op-small-fish-food), egg yoke and now microworms. I only introduce the food after about 2 days as I know they are still feeding on their yoke sac. I have some java moss in there and I am trying to culture insuforia, but right now it's not ready. They don't seem to be eating at all. I am literally pipetting the microworms in front of them (I have one about 3 days old right now) and nothing. In fact, they swim away

Any advice would be great. Right now I have some more fry on the way. The fry are in a 5g tank with a heater and air pump, filled about 2-3 inches with water. I am changing 50% of the water ever few days and vacuuming up any uneaten food or detritus I see.

 

[Colin_T]

How are you transferring the baby fish to the rearing container?
Make sure the eggs or fry are kept in water at all times and don't use a net to catch them. Use a plastic container to scoop them out and move them.

If you are using egg yolk or liquid fry food, you have to monitor ammonia levels because that can go up very quickly. When you feed egg yolk or liquid fry foods, add a small amount to a small phial of water and shake it up, then pour the solution into the rearing tank. You want the water to turn milky cloudy.

I would be doing a 75-90% water change each day using water from the adults tanks.

You can raise the water level up to 4-6 inches and have gentle aeration.

If you don't have infusoria ready you can add a heap of live plants from the main tank and there might be enough on that to keep the fry going.

 

[Byron]

I have fry from my various cories regularly and I just leave it to nature so only a very few survive. If you have them in an established tank with several chunks of wood and plants (moss is ideal) they will find natural live foods. This will not likely be sufficient to raise all of them that hatch, but some will. The best food to add are dried leaves, such as oak, maple, beech, or Indian almond leaves some fish stores sell. I collect leaves every autumn in my back garden where I know they are free of all chemicals and pesticides; just rinse them off, and lay them out to dry, then bag them. Put a couple in the tank every water change; they will become water logged and sink. Leaves produce copious amounts of infusoria, and any fry (applies to all fish) with dried leaves in the tank will grow faster, always.

I don't do more than the above, as I am not trying to raise them specifically. But beyond the above, microworms seem an ideal food. My 10g tank has pygmy cories and aside from the leaves I add nothing else except the sinking foods like shrimp pellets, etc for the adults. It is amazing how quickly the fry learn to feed on the shrimp pellets.

 

[Emma_M]

Thanks for you replies! I transfer with either a little container or with a pipette that has the end cut off. I've added some more java moss and also raised the water levels. Water changes are hard because the main tank is at 80 and the fry tank is at 78... can I ask how you do such large temp changes without shocking the fry? I didn't use to worry about temp changes that much until I shocked a fish a while ago and lost it and now I am a bit sensitive to messing it up!

I've noticed the adults laying more eggs so I'm going to leave them in the tank and see what happens. It's just a few here and there.

 

[Colin_T]

You don't want temperature fluctuations with fry because it kills them. I had the water temperature in the water holding tanks and the fry tanks. Then I could water change without temperature changes.

How are you feeding the egg yolk?
If you boil an egg and remove the white. Then push the yellow yolk through a handkerchief (or some other fine cloth) into a small amount of water and shake it up. Then pour some of that into the fry tank. You want the water to go slightly cloudy. Put the water and egg yolk solution in the fridge when not using it, and use it throughout the day. Make up a new lot each day. When you take it out of the fridge, let it warm up a bit before using it so you don't add cold water to the tank.

If you use a liquid fry food, add a few drops to a small phial of water and shake it up. Then add that phial of liquid to the fry tank.

How is your infusoria culture going?
If you need more info on culturing infusoria you can check the following link.
http://www.fishforums.net/threads/back-to-basics-when-breeding-fish.448304/

 

[Byron]

The temperature mentioned is high for cories. You indicate you have Corydoras julii, but most "julii" in stores are actually C. trilineatus. But in either species, the upper limit is 78F (26 C) and they will both be better lower, mid 70's. This might explain the fry not eating and dying.

I don't think a minor temperature fluctuation of 1 or 2 degrees F would affect cory fry, probably the opposite. I have a tank of pygmy cories that spawn regularly and it gets a water change every week of over half the tank and the temp lowers a degree or two. But the constant high temp may not be so good; remember that higher temperatures mean harder work for the fish's metabolism, and fry are more delicate in this to begin with. And there will be less oxygen.

 

[Colin_T]

78F (26C) is fine for breeding Cories just don't keep the temperature there all year round. However, while the fish are breeding, leave it at 78F.

My Cories use to start breeding in summer when the water temperature hit 26C (78F) and continue while the temp went up to 28C (82F). In winter the temp dropped to 18C (64F).

 

[mikey11]

feed them live baby brine shrimp and they will gobble it down like a kid to candy......

 

[Byron]

78F (26C) is fine for breeding Cories just don't keep the temperature there all year round. However, while the fish are breeding, leave it at 78F.

My Cories use to start breeding in summer when the water temperature hit 26C (78F) and continue while the temp went up to 28C (82F). In winter the temp dropped to 18C (64F).

Interesting, as I have the opposite experiences. My cories, and there are some 12-15 species all wild caught (except the pandas) spawn throughout the year; a fry will sometimes appear, but more often I find anywhere from 1 to 6 or 7 fry in the canister filter when I clean it every 3 months. The tank temp is 75-76F (24.5 C) and each weekly water change lowers this by 1-3 degrees. In the summer during hot weather the room temp goes up to 78-80F (the air conditioner prevents higher temps) and naturally the water will rise during the day, but the spawning is no more than the rest of the year.

It is often suggested that if a species is difficult to spawn, doing a significant water change with cooler water will usually stimulate it into spawning. That doesn't mean raising the temp might not do the same, but for cories it is always cooler water being suggested.