i have 2 goldfish. First i had them in quite a small tank, about 12 gallons i think, then I moved them to a bigger tank, about 20 gallons because the female (i still don't know which) laid eggs, to my surprise (im a newbie, i didn't/don't know how to raise them). I kept the eggs in the smaller tank and kept the water aerated but they died a day or two after hatching. I think maybe the mould from unfertilized eggs killed them or something. I looked on the Net what to do, everyone tells you a different thing. Then in the bigger tank she laid more eggs, not so much though. this time I put them in a breeding tank in their tank. They started to hatch and swim around and i thought this time they might survive. i left them there on Friday afternoon and was away overnight and i came back 1pm the next day, Saturday and they had all disappeared, not only the ones that hatched but all the latecomer eggs as well (i had removed all the unfertilized eggs before). They can't have just died and disintegrated such a short amount of time...or could they? :unsure: Also, i did leave a TINY amount of crushed boiled egg for them, - surely it didn't go mouldy and engulf them with mould so that they died and then were filtered away - coz the egg was still there and there was no mould. when i left they were kind of swimming to the side of the breeding tank, like vertically, do you think they got out the slits in the breeding tank? the filter is not very forceful at all. i was so disappointed. no sites said anything about breeding tanks anyway. and they're so tiny, as big as an eyelash.
i mean i put them in there coz, i thought that would be good for them, a filter, gosh i must sound so stupid :( anyway the water is very clear, the PH is 7). maybe the temperature is the problem (still doesn't explain where they disappeared to). i live in South Africa. The tank doesn't have a heater, it stays at room temperature, about 26 Celsius. another thing is the tank is by a window, sometimes in direct sunlight, is that bad?
Please help!

When the fry become free-swimming, they need to eat tiny foods. That's the time when most fry die. If there's a lot of fungus in the tank from dead or infertile eggs, then it can also kill the fry. Methylene blue can be added to the water to kill fungus but the fry (and all fish) are sensitive to that so it's only for the egg stage (a day or two when the eggs are first laid).

Yes, eggs or fry that die can actually vanish within a day as fungus, bacteria, and microorganisms can eat them up that fast. If they were in a solid breeder trap (no water flow with the main tank), then the water quality would certainly be worse in there. Some egg could rot but that alone shouldn't have killed them. Fry are very sensitive. I've raised many fry but even I have a high mortality rate. I have never raised goldfish fry indoors though (just in my ponds).

Oh, you say they were swimming vertically. That's normally how fry behave for the first few days. They are not yet "free-swimming" but living off of their yolks for a few days. Once at the surface, they are free-swimming and need to eat. I now read that indeed you had a hard plastic type breeding trap with slits. You bet that fry can go right through those if the trap is not solid all over. You need a net breeder instead or put the fry in another tank or a pond. You could also cover the entire trap with pantyhose. The thing with net breeders that I've found is when I go to clean them out with water changes, I often accidently squish or hurt fry. For that reason, a separate tank is generally safer but more work.

Your temperature is fine and some sunlight can actually be good as it makes algae and microorganisms grow which the fry can eat.

My page on breeding is at http://www.fishpondinfo.com/breed.htm

Better luck next time!

Thanks for your answer.
i have some more eggs now, that i hope will live. :D They started hatching at 10 am this morning, now it's 2:50pm and almost all 30 are sort of swimming around or lying around , they have their sacs still on. When must i put food in? are they still feeding off their eggs? what should i feed them?

The fry will just hang around for a few days and make short spurts of attempted swimming. Once they are swimming and floating just under the surface (as opposed to on the floor or walls of the tank), then they will be ready to eat tiny foods. Goldfish fry are tiny. They can eat suspended algae, Liquifry (which may no longer be sold), commercial dry fry foods (not as good), live infusuria (mostly paramecium), and other tiny animals that you can't even see. If you have access to an active and healthy pond, that water may be able to feed them. Only use that if the fry are in a tank of their own. I hope you can find something to feed them!

thanks,
i have them in a net breeding tank in my goldfish tank now and am feeding them brine shrimp. There are only about 30 fry. there's one baby who can't really swim and another that doesn't swim very well like the others. the one that can't swim, i think the spine is a little bent, i guess it will just die later? i don't have the heart to get rid of it myself.

Most batches of fry have some deformed ones. Bent spines are pretty common. I've had danio fry with bent spines live into adulthood but they were never full size. Most will die young as they can't compete and are prone to other problems.