Small Daphnia culture

idris

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Failure #2
After another 24hrs, even more of the shop bought Daphnia were dead. So ...

Start #2.5
Again I was passing the LFS so decided to pick up another bag. I'm disapointed to say that my ambition for zero cost has gone out of the window as I have now speant a stomach churing £2.50. Whislt my children may have to go hungry for a few days as a result, I am looking at this as a long term investement. :oops:
The LFS had taken delivery several days previously, so the live:dead ratio in the bag was nowhere nearer 1:1 than 1:0, but there were a decent number still alive and advice seems to be start with a small number ... and to go back when they have a fresh supply would mean a special trip and a resultant contribution to climate change.

I syphoned out as many dead Daphnia from the second demijohn as possible (the one without grass) and only added live ones from the new bag. (I may add some organic matter later.)
For convenience and better temperature (early evening, before the cenrtal heating goes on - about 18°C) I'm going to run this all in the house again, which will mean no air pump, just increased surface area.
I'm also going to be focussing on food for a few days:
1) A new bottle of green water has been seeded, this time with brocolli stem and frozen peas, and 50% of the water from the previous bottle.
2) I've mixed up some yeast solution from 5g of quick yeast, a pinch of sugar (to activate it) and about 100ml of water from the aquarium. Only about 5ml has gone into the demijohn so far, along with about 100ml of green water. The result is slightly cloudy and I'll have a look at the water clarity in the morning to judge how soon to feed again.
 

jaypeecee

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Hi @idris

Please remind me about the water you are trying to culture the Daphnia in. Is it tank water, treated tap water, rainwater or what?

JPC
 

idris

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I've read the Caudata page, though not recently. There may be bits I could do with rereading. (Grrrrrrr ...)

The daphnia are in tank water.
The greenwater was originally pond water, but has since been diluted with tank water.
We do have a water butt, but I've never got into the habit of using it for anything but gardening.
 

Basviola

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I did not take the time to read all comments on this, but I just wont to drop five cents here, as I looked quite a bit into this some time back.

And the most important things I remember was this:

Some species of daphnia is less likely to collapse in a culture.
(Sorry I do not remember the name, but think it is the type that is among the biggest, that is the easier one to go with)

Airstone is essential

Overfeeding can collapse the culture.
About collapsing cultures, if they reproduce faster that what you need for feeding, it will obviously lead to a collapsing culture... So throw out daphnia or give away to friends if it gets to tight in there!

About feeding, most people have had success with yeast. And as mentioned only feed a little, and first again after water is clear again. Some reports good effect with 2 part yest to 1 part spirulina.
 

idris

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Thanks @Basviola I think that concurs with everything I've read, exccpt the airstone: an air line is beneficial (though not an absolute requirement) but an airstone can be a bad idea as they tend to produce fine bubbles which get caught in the Daphnia shells, float them to the surface, where they get stuck due to surface tension.
 

jaypeecee

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The daphnia are in tank water.
Hi @idris

I have a few questions about your tank water:

1. What are the KH and GH of your tank water?

2. Was your tank water first treated with tap water conditioner before adding to your tank? If so, which?

3. Have you ever used a snail killer treatment in your tank or any treatments that contain copper sulphate?

That'll do for the moment.

We'll get to the bottom of this.

JPC
 

idris

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The water should be fine.

1. What are the KH and GH of your tank water?
I couldn't give you numbers (and don't have a test kit), but we have pretty hard water round here.

2. Was your tank water first treated with tap water conditioner before adding to your tank? If so, which?
Every water change (10%) is treated with conditioner in a 25L canister before adding to the tank - off the top of my head, I think it"s AquaCare Tap Water Conditioner. Whatever it is, I know it claims to deal with "heavy mwtals" so that shouldn't be a problem.

3. Have you ever used a snail killer treatment in your tank or any treatments that contain copper sulphate?
Only water, dechlorinator and ferts have ever gone in this tank (9yrs) and no ferts in the last 2-3yrs. (I've always had assassin snails to combat .... well ... snails.

The greatest risk with the tank water is probably NO3, but as I've been getting back into the habit of regular water changes (even if not filter media flushes) every week, and it a well planted tank with relatively few fish, even that is quite unlikely.

If you're thinking about contamination ...
The demijohn were second hand, and probably used for wine making. There was some residue at the bottom that I couldn't clean out, but have no idea what it was. I tried both formic acid and bicarb to remove it but neither made much difference. The jar was very thoroughly rinsed afterwards and no detergents were used.
 
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dw1305

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Hi all,
Airstone is essential
most people have had success with yeast.
I think if depends what you want from your cultures. If you don't mind lower productivity you can use a less polluting food source.

You don't actually need added air, you just need to keep the water quality reasonably high, but this is difficult when you feed with yeast.

I've kept the same cultures (for at least the last fifteen years) and you can do this if you avoid boom and bust. It is a bit like keeping free range Chickens, rather than broiler house ones.

Daphnia feed by sieving out particles of a certain size from the water column, they don't differentiate what that food particle is. Green algae, yeast, gram flour, spirulina powder, paprika etc. all work because of the size of the particle. If you add dried grass it generates algae, rotifers and protozoa, of a suitable size, which the Daphnia can then eat.

cheers Darrel
 

jaypeecee

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You don't actually need added air, you just need to keep the water quality reasonably high, but this is difficult when you feed with yeast.
Hi @dw1305

When you make a statement like that, Darrel, I sit up and listen. So much so that I had to delve deeper. And I found the following:

https://setac.onlinelibrary.wiley.com/doi/abs/10.1002/etc.5620110311

So, whether it's Daphnia magna or Daphnia pulex, provided that dissolved oxygen is greater than 2.1 mg/l, all should be well. That's a pretty low figure! Of course, it could conceivably drop down that low when feeding with yeast or, indeed, anything else with a high BOD. And that's when aeration must surely help? With reference to your comment that "you just need to keep the water quality reasonably high", would you care to elaborate?

JPC
 

dw1305

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Hi all,
So, whether it's Daphnia magna or Daphnia pulex, provided that dissolved oxygen is greater than 2.1 mg/l, all should be well. That's a pretty low figure!....With reference to your comment that "you just need to keep the water quality reasonably high", would you care to elaborate?
Yes, agreed these things are all relative. We have figures for the Daphnia species etc. because they are used in water quality bioassay etc. That is actually a reasonably higher level of dissolved oxygen for a species that naturally lives in eutrophic still waters. The situation is slightly different in streams etc., where organisms generally <"have higher oxygen requirements">. Daphnia are much more sensitive indicator of contamination by <"pyrethroid insecticides"> etc. which is why they are used as a bioindicator.

You can probably visualise situations where you would naturally find Daphnia exposed to low oxygen/high CO2 levels. You could have a warm, stil, night and pond water with a lot of algae present. Where people are using algal ponds ("High Rate Algal Pond") they deliberately add CO2 at night to try and <"reduce zooplankton numbers">.
it could conceivably drop down that low when feeding with yeast or, indeed, anything else with a high BOD. And that's when aeration must surely help?
I think if you are feeding yeast you just have to be a lot more rigorous with water changes, cleaning and thinning etc. Adding a snail helps. I don't see any problem with added air as long as you don't have too much water turbulence, and the higher oxygen levels it produces are definitely a bonus.

The <"standard lab. procedure">, (to maximise production), is to feed with a mixture of Chlorella and yeast.

cheers Darrel
 

jaypeecee

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Hi @dw1305

Many thanks for your reply.

You've answered all my questions.

BTW, I already have a copy of the Reading University SOP. But I chose not to reference it as I thought it may deter people from culturing Daphnia!

JPC
 
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