Daphnia culture

[Magnos]

I searched and didn't find a thread on this. Sorry if it's a repeat. I have a daphnia culture that's been running good for about 2 weeks. I'm starting to see black (eggs?) Floating at the top. Is this indicative of another issue?

 

[Colin_T]

Black egg cases usually sink to the bottom. They can remain dormant when the pond/ waterbody dries out and after several months of dry, the egg sacks will hatch when they are submersed in water again.

If the female Daphnia have the black egg cases in their body, the females have been kept in warm water and are preparing for the end. As the water warms up, the females develop the egg cases and shed them into the environment so the next generation will be able to start after the pond dries up and then refills the following year. If the water doesn't get any warmer, the females can live for a while and might start producing live young again.

 

[Magnos]

Black egg cases usually sink to the bottom. They can remain dormant when the pond/ waterbody dries out and after several months of dry, the egg sacks will hatch when they are submersed in water again.

If the female Daphnia have the black egg cases in their body, the females have been kept in warm water and are preparing for the end. As the water warms up, the females develop the egg cases and shed them into the environment so the next generation will be able to start after the pond dries up and then refills the following year. If the water doesn't get any warmer, the females can live for a while and might start producing live young again.

But black eggs on the surface of the tank?
So I should increase the temperature?

 

[Colin_T]

no, do not increase the temperature, they do best in cold water (5-15C).

no idea why the eggs are floating. scoop them out an let them sit in a paper bag for a few months, then add them to some green water when the weather is cool.

 

[GaryE]

Here in Canada, black eggs mean mosquitoes have been by. Their eggs float.

They make good food if you give them to the fish before they have wings. They are more nutritional than daphnia. you're in New Jersey, so I'd expect conditions to be closer to here than to Colin's Australian experience.

I screen my daphnia cultures to keep them out.

 

[Magnos]

Oh crap!!! It's in my basement!!! My wife will kill me if we get mosquitoes

 

[Colin_T]

Before you panic, how big are the black eggs?
Daphnia egg sacks are about 3mm long x 2-3mm wide and shaped almost like the number 8.
Mozzie eggs are the size of dust.

Post a picture if you can.