Mysterious 3 week die off

[ekocak]

I've had 3 clutches of eggs from the same female. It's her first time laying, but she is 3.5 years old and nearly a foot long. All of the eggs develop normally, hatch and feed. Then all of the clutches, right around the 3rd week, pretty much overnight die off. I have tried changing foods (I started with bbs, thinking that it was fouling the water too fast and switched to culturing my own daphnia), I've made sure the temp is a consistent 64 F, and I've done daily water changes, with the water down to about 1.5 inches in a ten gallon tank. I'm scratching my head. Is it something genetic? They all seem fine and then suddenly every single one is dead. Something bacterial or viral? It doesnt seem to be water quality, I use RO water (I have a system for my reef aquarium), and the daphnia seem as happy as ever, I would think if it was water quality it might affect them as well. Any ideas?

 

[auntiejude]

It could be any one of half a dozen reasons larvae die:

1. water quality problem #1. Ammonia builds up very quickly in larvae tubs, you might find more water helps, or more frequent changes. Make sure you remove uneaten food.
2. water quality problem #2. RO water doesn't have any minerals in it and axies like hard water. try adding some Holtfreter's salts or remineraliser. RO water will leach mineral out f food and the larvae, leaving them deficint in Ca and Fe.
3. Genetics. They have a fatal gene that causes them all to die. Or they are weak genetically. If they have the same father each time this will continue until you get a new sire.
4. Temperature swing. A large change in temp can kill larvae, up or down.
5. Bacteria. It build up on the bottom and walls of tubs, and you really need to give it a good clean every time you change the water - hot water and a paper towel.
6. Bad luck. It happens.

 

[ekocak]

Thanks for your thoughts. I guess the thinking was by keeping the water level low it increased the likelihood of daphnia swimming near the larva, but obviously, less water means less time before an ammonia spike. Maybe I should try increasing the amount of water next time. I test the water every few days and it seemed on target, but who knows...

 

[Brigitte]

I have no idea if this applies but I also had a mysterious die off recently and after considering all of the variables compared with the last time I raised a clutch (successfully) the culprit seemed to be the plastic tupperware (that disposable tupperware from the grocery store) I bought to hold the larvae this time while they were small. I suspected it leached chemicals that killed the larvae. I have since then read posts that confirm this possibility from others. There were two (gulp) survivors of the 40 larvae and they are doing well in their glass dishes for the past few weeks.
Hope that helps.
I'm all glass now.