How to improve the survival rate of my fry?

[Joost]

Hello all

For a while now I have about 100-150 corydoras eggs per week from different breeding groups. Usually most eggs hatch, and a large percentage of the fry stays alive.

My question is though: Often I see a few of these babies swimming or sitting around with tiny air bubbles in their tummy. Usually later that day those which had the bubbles earlier have died. Does anyone know how to prevent this form happening, or what I am doing wrong?

The first few days I keep the fry in 1 or 2 liter containers with an airstone in it.

The difference in temperature between the water and the air above the tank is somewhere between 1-2 degrees Celsius. The water being a bit warmer.
Or could this be caused by the bubbles the airstone produces in the water?

Thanks

[Joost]

As an experiment I removed the airstones from two fry containers today.

[Thoth]

I just had a my first batch of eggs hatch about 3 weeks ago. I removed the adults from the 10 gallon and left the eggs with a HOB filter w/sponge over intake. I didnt use an airstones or fungus treatment. Lost tons of eggs to fungus and the further away from the filter the worse the fungus. I only had one baby with an air bubble in his stomach, so out of 15 or 20 that hatched thats ~5%. How many fish have the air bubble issue?

and nice angels video.

[Joost]

I usually loose some eggs to fungus, but really not that many. I assume that those aren't fertile. I try to keep very clean water though.

In the last batch before I posted my question here I lost about 20% to these air bubbles. More than usual. But then now I realize that the airstone in this container was not attached to my regular air system, but to a different air-pump. Perhaps the airstone ran faster and caused the higher loss to bubbles in the tummy rate?

[MatsP]

My guess would be that the gas bubbles in the tummy is not externally formed, but formed by internal bacterial infection. I'm not 100% certain, but I'd guess that it's "flatulence". Corys do take on air from the surface, and this doesn't kill them.

--
Mats

[Bwhiskered]

Try treating the breeders with Metro. I have not had this problem with corys but a similar problem with other species where the fry hatch but the belly bloats and they die instead of becoming free swimming. The bacteria is passed through to the female to the eggs. I have seen this problem with angels, discus and plecos. It may be your problem. An alder cone or an oak leaf with the eggs or fry may also help.

[Joost]

Bacterial infection is a possibility that I hadn't considered yet. The tummies don't bloat up all that big, but you can see tiny air/gas bubbles through the belly skin. Metro isn't sold out here anymore. Prohibited by government regulations. I will try a Cattapa leaf, and see if that works. In my experimental containers without airstones so far I have only had a couple of more babies with the bubbles, no big numbers anymore. But still the reason could very well be an infection. I will keep you guys posted on the results with Cattapa leafs.

[dw1305]

Hi all,
I think the air bubbles are as a result of internal bacterial action as well.

An alder cone

I'd definitely go down the Alder (Alnus cordata/incana/glutinosa) "cone" route, I just put 3 or 4 cones in the fry trap. Oak (Quercus)/Terminalia cattapa leaves will also work, but alder cones are very easy to work with. Last years Alder cones will be falling from the trees now (as they start to come into leaf/catkins) in the spring.

cheers Darrel