Small Daphnia culture

[idris]

Having decided to try culturing some live food, although Vinegar Eels sound easiest, I thought I'd have a go at Daphnia.
There's no shortage of info online, so I won't go through much of the background - this is just a here's what I tried journal, and ultimaely a whether-or-not-it-worked journal.
My goal is to try to do this both on a small scale, and for as little money as possible.

As we have a garden pond ...



... this is where I sourced some water from, hoping it would yield enough Daphnia to get started.
The pond has a few fish in it, and being October, I didn't expect a large number of Daphnia from the start, but a bucket of pond water sat in the garage for about 3 wks with a heater in it, set to about 20°c, in the hope that the warmth would accelerate the Daphnia's reproduction.



Having borrowed an old microscope, with regular checking, I (think I) managed to identify daphnia in water from the bucket after about 2½ wks.



They're tiny little ****ers and don't stay still under the microscope, but I'm pretty sure I found some Daphnia, along with (probably) Cyclopse, Ostracods and Midge larvae.

In the meantime I filled a 2L plastic bottle with more pond water, to use as a green-water culture, with which to feed the Daphnia, and sat that on a window sill. That turned green, then cloudy, but I wasn't happy with that starting to smell a bit sulphorous after a couple of weeks, and I hadn't yet spotted any Daphnia, so I threw that out and started again.
And a request on Freegle got me a couple of free 5L demijohns, in one of which I will try to seed the culture.

Largely at Darrel's suggestion, I collected some dried grass from the edge of a local field, and have tied a small sheaf together with cotton. (I've tied it up just so it's easier to get out if I decide to.)



As I understand it, the grass helps both stabalise the water chemistry and provides a food source for infusoria and thefore the Daphnia. (Please feel free to correct me on this. 😉)

On a cold, sunny, November morning, I filled half the demijohn with water from the bucket, and over the next half hour or so (so as not to shock any fauna) topped it up with water from my aquarium.



Next:
I'm in two minds about the degree to which I'll try to feed any Daphnia (and anything else that's in the demijohn). I can't spot any obvious fauna in the at the moment, but once I can, I'll try feeding with just green water. Depending on how that goes, I may try yeast.

 

[Gill]

Daphnia are so easy to look after. Feeding wise: Green Water, Spirulina powder and Bakers yeast is great(tiny amount and once water is clear again, they have eaten all the yeast).

 

[jaypeecee]

Hi Folks,

I've cultured Daphnia. The water in which they are kept needs to be oxygenated. If I remember rightly, their body starts to turn red (from clear) when oxygen level gets low. But, it's better not to use an air stone that produces a fine mist of bubbles. Apparently, the bubbles can get trapped inside their carapace and kill them. Unfortunately, I lost a whole batch of Daphnia this year back in August when we had the heatwave. They are not happy if the water temperature goes much above 25C. One other thing is that light encourages reproduction. Oh, and another, they are very sensitive to contaminants in the water. Tank water in which fish have been kept free of any medications should be fine.

JPC

 

[jaypeecee]

But, it's better not to use an air stone that produces a fine mist of bubbles.

I meant to add that airline tubing (6/4mm) connected to an air pump at one end and open-ended at the other is what is needed. Running this into the water at about 1 bubble per second should do the trick for a 2 litre container. Scale up accordingly.

JPC

 

[idris]

I've only spotted a couple of Daphnia in the demijohn so far and the water is still coloured, so no feeding yet.

I'd read that about oxygenation, but unless I've mis-remembered / misunderstood, Darrel was suggesting that was less than necessary. I figured I'd start without and see how it went.

I an wondering whether it's worth removing the plant matter that was in the pond water and has sunk to the bottom. Its a source of decay (negative) but may promote algae which the Daphnia will feed on (positive).

 

[jaypeecee]

I've only spotted a couple of Daphnia in the demijohn so far and the water is still coloured, so no feeding yet.

I'd read that about oxygenation, but unless I've mis-remembered / misunderstood, Darrel was suggesting that was less than necessary. I figured I'd start without and see how it went.

I an wondering whether it's worth removing the plant matter that was in the pond water and has sunk to the bottom. Its a source of decay (negative) but may promote algae which the Daphnia will feed on (positive).

Hi @idris

Are you certain that the couple you spotted are actually Daphnia? I saw your video but it was a tad out of focus. I'm not being critical. It's not easy 'filming' Daphnia. They are unmistakable and swim with a jerky movement. I took the easy route with my Daphnia by buying live Daphnia from my LFS. For less than a quid, it was a no-brainer. It goes without saying that it's essential to use at least a magnifying glass to check any that you buy. You don't want to find other unwelcome critters in the bag! Almost from day one, the population of Daphnia grew and, at the same time, I was feeding them to my fish.

JPC

 

[idris]

I've identified Daphnia from the bucket with a microscope.
I can't guarantee what I've since spotted (with a magnifying glass) in the jar, but they look to be moving in the right way. They're bigger than Ostracods, and don't move like Cyclopse.

I could probably get some from a LFS (though I've not seen them specifically amongst the live food) but I wanted to try seeding a culture from the pond I may resort to buying some if this fails or takes too long.

 

[idris]

6 days on, and I couldn't initially see any life in the demijohn.
But then I spotted a significant number of creatures in the bottle I was culturing as green water.
A little more patience and I spotted a couple of inverts in the demijohn as well.

The reality is there's not a great deal of difference between the two containers at the moment - the water in both is green and both have decaying organic matter in them. So it's probably largely chance at the moment.

There seem to be three discernable types of inverts I can spot with a magnifying glass.
The first are visible as little more than dots, and a fraction of a mm long. These are the most prolific.
The second (left below) are the scarcest, and I may be Daphnia or Copepods. If anything, they have a slightly pink hue, which I think is evidence that they may be Daphnia feeding on bacteria, rather than algae.
The third, (right) looks more opaque and I'm pretty sure are Copepods.

The second and third are no more than 1mm long, and those on the left follow a slightly more eratic path.

 

[Guest]

Could be male and female cyclops.

 

[zozo]

Daphnia feeding on bacteria, rather than algae

They feed on much more than algae alone. 🙂 I keep Daphnia in a 100-litre tub in the garden that only contains dead leaf litter. The water is always crystal clear and all year round Daphnia in it. It's still is boom and bust, but there's always something in it. Sometimes it bursts from Daphnia other times it's less and it keeps going up and down like this. I never ever look after them with extra food or such, it's completely self-sustaining. I only take out some leaves that fell in if it looks like too much. The decaying leaf litter in it seems to provide enough food for them. At times the tub looks empty, but then they are all on the bottom under the leaf litter, a little wigle with the net to stir them all up ready to catch.

 

[jaypeecee]

Could be male and female cyclops.

Those were my thoughts entirely.

JPC

 

[MJQMJQ]

From the video that looked like seed shrimp.If u can find greener dried grass it is better(higher nitrogen content for the algae) .The one with the pinkish hue is probably daphnia.
Low oxygen usually affects an entire population, coloring all animals reddish. https://www.ncbi.nlm.nih.gov/books/NBK2042/
Do you have an air stone in there?Green water is the most easily cultured with exposure to sun 😉

 

[idris]

The "video" is only 3 frames and relatively low magnification, so don't read too much into it.

Greener dried grass? I'd understood that the stuff put in rodent cages was ideal, and I was under the impression that was definitely not green.

There isn't an airstone as there isn't a convenient mains socket near a convenient windowsill.

 

[dw1305]

Hi all,

Greener dried grass?

I think some people use the dried grass pellets you get for Horse, Hamster, Rabbit food etc.

It is just a nutrient issue really, greener grass will have more sugars and proteins etc., but more power to pollute (a higher BOD).

I use lawn cutting (in the summer) in buckets of water to encourage Mosquito larva and Bloodworms, they don't need high quality water, so it doesn't matter if you end up with low oxygen.

I don't like my Daphnia cultures to be too productive, you tend to get the boom and bust, mainly because Daphnia have fairly high water quality requirements. Adding dried grass (hay) makes the cultures tick over for longer.

cheers Darrel

 

[jaypeecee]

There isn't an airstone as there isn't a convenient mains socket near a convenient windowsill.

Hi @idris

You could try a battery-powered air pump. It wouldn't have to be powerful as you don't need the airstone as I explained previously. Without aeration, your chances of success are not good. I guess you could try a wide-topped shallow dish. This will maximize oxygen diffusion into the water but it may need to be topped up frequently to compensate for evaporation.

Good luck!

JPC

 

[idris]

Failure #1 ... and possibly #2

After a week+ without quite the progerss I'd hoped for, I happened to be passig a couple of LFSs and figured I might as well buy a bag of Daphnia as a comparison.
The first LFS had them in the fridge and it was dificult to see any movement in the bag. There had been a fresh delivery 48hrs previously, so I hoped to see some life, but being refrigerated could easily account for sedated critters. I went to the other LFS, whose bags were on the counter and filled with much more active Daphnia. (And they were 25p cheaper ... hey ... we're living in a time of austerity!)

Back home, as I had a second demijohn, I introduced the bag of shop bought Daphnia into freshly siphoned tank water in a similar way to introducing new fish. Warming up, then sowly adding just a little tank water. Working with a much smaller volume of water made this harder than with fish, but it was better than nothing.
I'd guess that there were easily more than 100 Daphnia bouncing around.

First thing of importance is that seeing bought Daphnia next to what I had from the pond, it was obvious that what I've been looking at in the first jar were absolutely not Daphnia. Daphnia are significantly bigger and can easily be identified with the naked eyer, whereas what I've mostly been observing till now could only be identified with at least a magnifying glass. (I'm still pretty sure I've identified Daphnia from the pond water with the microscope, but there were certainly not in significant numbers, compared to the Copepods.)

For various reasons, I set up the second demijohn in the garage. It's well insulated, so cool, but not cold, has some direct light, but not as much as in the house, and there is the option to plug in an air pump.
The one air stone I had produced a lot of small bubbles. Removing the airstone resulted in a lot of big bubbles. From what I've read, small bubbles are a bad idea, so I opted for big bubbles. The downside was that it made the water quite turbulent.

Come the morning, most of the bought Daphnia were dead. I'd estimate about 30 were left.



Meanwhile, the bottle intended as a green water culture had pleanty of cyclopse, and the first demijohn had pleanty of algae.



Some of the green water has been "fed" to the remaining shop bought Daphnia, and that will go back in the garage. If I can find an air valve, I'll also try to restrict the amount of air bubles / turbulence, just so I'm only changing one variable at a time.
I've also tried to remove as many of the dead Daphnia as possible. They could help nurish algae to feed the healthy Daphnia, or they could polute the water. I don't know which is more likely at this stage.

 

[dw1305]

Hi all,

The one air stone I had produced a lot of small bubbles. Removing the airstone resulted in a lot of big bubbles. From what I've read, small bubbles are a bad idea, so I opted for big bubbles. The downside was that it made the water quite turbulent.

Come the morning, most of the bought Daphnia were dead. I'd estimate about 30 were left.

It is the turbulence, they don't like it and it stops them feeding.

If you add air it needs to be a very slow bubble rate. Personally I would worry about adding air, I'd just drop the water level so that it is in the wide bit of the demijohn and improves the surface area to volume ratio.

cheers Darrel

 

[idris]

Hi all, It is the turbulence, they don't like it and it stops them feeding.

I wondered whether that was the cause.

 

[jaypeecee]

Hi @idris

I cannot resist trying to help you. So, what is the temperature of the water that your new Daphnia are in? It may also be that, being in your garage, light is now too low. As regards the airflow, I originally suggested 1 bubble per second. In order to achieve that, you can fit a flow adjuster in the airline. You'll be able to see if the Daphnia are not getting enough oxygen by their colour.

You can still be successful with the 30 Daphnia that you have left.

JPC

 

[idris]

I cannot resist trying to help you.

Don't feel bad about that at all!!! Input from those with experience us very welcome.😀

So, what is the temperature of the water that your new Daphnia are in?

I've not measured that yet. As I understand it, low 20s C is about right, depending on the variety. (Though I have no idea whether I've actually got Pula or Moina.)

It may also be that, being in your garage, light is now too low.

It's not as dark as most - just not as bright as the kitchen windowsill. Considering others have talked about harvesting Daphnia from water butts, I'd be surprised if that killed off so many in less than 24hrs. I was under the impression that light was as much about photosynthetic infusoria as the actual Daphnia - yes/no?

I originally suggested 1 bubble per second. In order to achieve that, you can fit a flow adjuster in the airline.

I remembered your 1 bubble recommendation, and was a bit concerned about the turbulence, but it was a choice between turbulence or small bubbles or no air in the first 24hrs. I just didn't anticipate turbulence having such a devastating effect so quickly. I've since dug through old boxes and found a valve which is fitted to the air line. It's now at slightly more than one bubble per second, but the Daphnia aren't getting buffeted around and are swimming freely. Depending how they do over night, I may dispense with the airline, increase the surface area (as per Darrel's suggestion) and move the jar indoors.

You'll be able to see if the Daphnia are not getting enough oxygen by their colour.

They are quite pink at the moment. How quickly are they likely to loose that with appropriate dissolved oxygen levels?
I know O2 levels improve with decreased water temp - how significant is that likely to be? My guess is it's probably between 5C and 10C warmer in the house, depending on time of day.

You can still be successful with the 30 Daphnia that you have left.

Yeah - I've read of sustainable cultures from as few as 10, so I'm not giving up on this batch yet.😀