New hatch of Rachoviis

[wcknight]

Finally, some limited success at hatching a batch of killies....

After getting only 1 of 5 Guntheri to survive, and then getting only 1 fry (that died within a week), I got 80+ fry from a batch of 100 eggs.

There were probably a bit more than 100 eggs, but the spawn was a huge relief after having so few the first couple of times. I have them separated into 3 containers... Some are very very tiny and I doubt they will survive.

But even if only 25% make it to adults, that would leave me with 20 + fish to breed...

So far only feeding with micro worms, with BBS being hatched soon, and vinegar eels maybe tonight or tomorrow..

regards,
wes

[wcknight]

After almost 2 weeks, the number of fry is greatly diminished... by over 90% ... where they are and what happened to the rest is anybodies guest. I suspect that most were too tiny to survive, not enough microscopic food to support the brood.

Out of 3 containers each having between 20 and 30 fry, only a couple in each are still alive. These are a bit smaller than baby guppy size, but have full stomaches.

Is this normal ? to have such a high mortality rate ??? I've been feeding Microworms and vinegar eels once or twice daily. Are these still too big for the newly hatched fry ?

Wes

[stormhawk]

It could be a whole host of reasons to explain the high mortality rate. Sometimes these critters just die for no apparent reason. For nothos my guess would be velvet that became the mass killer.

[whuntley]

I did not keep accurate records, but back when I was quicker to whip out the microscope, I learned that something like 90% of the baby mortalities, when the die off was massive, was Velvet disease.

It isn't just Nothos, but I suspect they are more vulnerable than some other Genera.

How much salt was in your baby Notho container?

Wright

[timebomb]

But even if only 25% make it to adults, that would leave me with 20 + fish to breed...

Remember what they say about counting your chickens before they are hatched, Wes

Compared to some Killifish fry, the N. guentheri fry are actually quite big. So I don't think size was the problem. Unlike what most Killifish breeders do, I feed my fry sparingly and rarely do I have massive die offs. You're feeding twice a day. I usually feed once every 2 days and the only food I give is baby brine shrimp. I kind of suspect the heavy feeding could be the reason for the high mortality rate. Uneaten food in the trays can contaminate the water and kill the fry.

I don't think it could be velvet disease because if it were so, you would probably have a 100% death rate and not just high mortality rates. Velvet spreads quickly in a small container and fry are too weak to resist the parasite.

At 2 weeks old, N. guentheri fry, being fast-growers, should be fairly large. If you can't find any dead bodies, chances are there's a predator in the trays. Did you check for Dragonfly nymphs?

Loh K L

[Diapterondave]

I am currently no longer using any bbs. I now have so much Moina, rotifers, greenwater, and (when I get around to collecting at my buddies lake) Cyclops. The Moina I sieve with a 400 micron down to 100-micron sieve and I get Moina of all size for my fry and adults. I start my small fry off on greenwater, rotifers and moina. I also feel the fish relish Moina and prefer it to other Daphnia sp. The greenwater makes the Moina and Rotifers boom ensuring continued food for the fry. As the Moina multiply you’ll have baby Moina that will also keep feeding the fry. I have found this to be effective for me especially with sensitive fry. As Loh pointed out water loaded with organic waste will lead to serious problems. This method is so natural. I am raising some D.abacinum fry that I believe have done so much the better due to the great food. I aso agree with Wright velvet is a very common culprit in fry mortality. And this can be prevented by improving their environment. I also think it can be very easy to feed bbs and over feed and pollute such small tanks. With Moina I dont care how much I feed. They will filter and clean my baby tanks any way.

[wcknight]

The fry were N. Rachovii, so, many were very very tiny.

The water was from my holding tank, which gets about two teaspoons of salt for every two or three gallons when I do my water changes.

It looks like 4 will survive in total. I have not seen any dragon fly nympths or any other predators, I have a couple of small snails in each container.

I will try to set up a tank with green water and infusoria before trying the next batch, feed less often and see what happens. Thanks for the advice !

regards, Wes

[Diapterondave]

Wes,

I do my infusoria cultures with a banna peel or a few grains of rice in a gallon jar. Be carefull not to much too much orhanic material or youll end up with just a stinky mess ( bacteria soup) 1'4 of a banna peel is just right for a gallon jar and 2-3 grians of uncooked rice is just fine for the gallon jar as well. ALso add lots of java moss. The key is balance. Goo dluck

Dave

[wcknight]

Thanks Dave, about how much in advance do you start preparing your culture, or do you keep one on-going ???

BTW, what is Moina ? and how do you sieve them down to size ?

[stormhawk]

Moina is a smaller version of the regular Daphnia. They're cultured in Singapore in massive amounts for the trade. You'll need a micron sieve to get them in the sizes you want. I don't sieve them, I just give them a quick rinse and feed them directly to the fry. The fry pick out the tiny ones themselves and the adult Moina simply produce more babies all the time.