Questions on Daphnia

[Neptune, the Mystic]

Brought daphnia for the first time in a bag from a LFS. Am I supposed to use up all within the same day or can be it left in the bag floating in the fish tank for the next day without spoilage.

It is possible to overfeed the fish if all is released into the tank at one go?

There is also the added problem of having to leave the water pump switched off for the duration the feeding which can be very long otherwise the minute crustaceans will be drawn into the filter system via the outflow.

[stormhawk]

If you have a filter running, especially a power filter, then turn it off for a minute or so while you feed the Daphnia to the fish, after which you can turn it back on. You must sieve the Daphnia from the water in the bag they came in, then rinse them with tank water and then just add to the tank directly. Depending on how many fish are present in the tank and the amount you purchased, a typical bag worth 50 cents goes a long way. Just sieve enough for the fish to eat in one go. You can do this several times over a few hours since the critters are so small. Several will get sucked in by the filter but this is normal.

You must transfer the remaining Daphnia to a bigger plastic tub, add some tank water and place a light over it. Otherwise they will die in large numbers within the first few hours. If left in the bag floating in the tank, they might die from lack of oxygen. With no light source, I find that they die faster. I usually manage to keep 50 cents worth of Daphnia alive for at least 2-3 days. If you bought a larger amount, then use a bigger container. Make sure it's not a brand new container. An old plastic tub or tank will do. Bigger surface area is better and no aeration needed.

[Neptune, the Mystic]

Stormhawk, thanks for the tutorial. I now know what to do next time.

[lucasjiang]

Dont forget to remove the dead daphnia from the container which you use to store the remaining daphnia. Otherwise, the dead daphnia will cause an ammonia spike and the remaining daphnia will die at an even faster rate. If you want to prolong their lives even longer, you can add some greenwater to the container.

[stormhawk]

If removing the dead ones, just need a simple airline tube or a turkey baster/syringe thing to suck them up slowly. Leave a few dead ones in the container. The bacteria generated from the decaying bodies serve as food for the living daphnia. Greenwater is good, but since I can't keep a culture going strong at home, I just let them feed off the bacteria and any algae present in their tub. Often, they come with algae spores in the water, mostly green and hair algae. A friend of mine feeds his daphnia culture with a suspension of powdered milk.

[Neptune, the Mystic]

Haha, I was about to ask how to remove the dead ones if I can tell them apart. That answered, do they separate naturally on their own, i.e. those at the bottom and seem lifeless are the ones to be removed while those at the surface are healthy? (I no longer have the culture to ascertain that).

[lucasjiang]

Haha, I was about to ask how to remove the dead ones if I can tell them apart. That answered, do they separate naturally on their own, i.e. those at the bottom and seem lifeless are the ones to be removed while those at the surface are healthy? (I no longer have the culture to ascertain that).

Yes, that is the case. The live ones will be at the surface attracted to the light whereas the dead ones will all sink to the bottom.

[stormhawk]

At the bottom of the container you will find the dead ones and any eggs that the rest may have laid, along with their waste matter and any other detritus present. The eggs will be small blackish specks in the mess at the bottom. If you dry the stuff at the bottom and wet them again later on, you may find some newborn daphnia.

[Neptune, the Mystic]

Oh, I see. (I missed reading the last post).