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Any ideas to refine this moina/daphnia culture approach?


memorywrangler
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I've been struggling to sustainably and densely culture moina for a year or so and I recently happened on this approach which seems promising. 

  1. I have two 2.5-gallon containers that I started with some moina and old aquarium water. 
  2. They are lit by a really powerful LED grow light that runs 12 hours/per day.
  3. As you can see, I have a lot of algae growth
  4. And I have really great crop of big, fat moina.
  5. Since I got the light, I haven't been feeding them anything.

To be clear, I don't think it's technically green water, although it has a green tinge.  Most of the algae are on the sides, but it seems that somehow the moina are eating it.

Despite the current bounty, there are some problems.  Most notably, the algae grown is really out of control:  It pearls a great deal it took the water from Nitrate/nitrite = 40/7 to 0/0 zero in a day or two.  This makes me think it's ripe for a crash.  The other problem is that takes a lot of power:  the light is 120W so 12 hours is about 1.4kWh/day which is about $200/year.

So my next move is to reduce the photoperiod (unfortunately, the light is not dimmable).

But I'm curious if anyone else has suggestions, has tried anything like this, or has any other ideas on improving the setup.  I have a few specific questions, too:

  1. Are the moina eating the algae that grows on the side, or do I effectively have a very pollute, weak green-water culture?
  2. Could I just feed these cultures Easy Green?  Is there something better/cheaper?

Thanks.

 

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On 2/25/2023 at 10:36 PM, memorywrangler said:

Are the moina eating the algae that grows on the side, or do I effectively have a very pollute, weak green-water culture?

Daphnia do this for sure. I'm guessing Moina does it too.

On 2/25/2023 at 10:36 PM, memorywrangler said:

the light is 120W so 12 hours is about 1.4kWh/day which is about $200/year.

They actually do better in low light. I'm guessing your success here is from the light creating a self sustaining food source and better water quality. There's probably a limit how much you can grow this way but maybe that's all you need. If it works, it works.

On 2/25/2023 at 10:36 PM, memorywrangler said:

Could I just feed these cultures Easy Green?  Is there something better/cheaper

I've been using these two products to grow greenwater. Together they cost about $15 and they'll last for years:

PXL_20230217_022220175.jpg.4046da5603b770d34a91346290684531.jpg

I usually  add 1 mL of the ammonia and 0.25 mL of the PK fert per gallon of water at a time which makes about 5 ppm of NH3 and PO4. I do that a few times until the greenwater gets nice and dark. I test for ammonia to make sure it's mostly gone before adding some Moina. Then I start a new batch of greenwater at about this time. I've done this in anything from 1 quart jars to 5 gallon tanks. 

PXL_20230101_022632983_exported_stabilized_1677481710029.gif.ea1cfbe772e68110051e15bbb1d63dbc.gif

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  • 2 weeks later...
On 3/9/2023 at 4:43 PM, Lowells Fish Lab said:

That's some gorgeous green water. I assume you figured this out over time but have you found P and K to to be critical?

Depends how dense you want your greenwater. I didn't record this but at one time I had a tank of greenwater that didn't get any PK next to one that did. The no PK tank grew fine, it looked like a normal greenwater culture, although it didn't get as dark as the PK tank.

After some time a few of my Moina jars died off the day after adding the usual amount of no PK greenwater. Turned out the ammonia in the no PK greenwater tank had built up past 30 ppm if I remember right while the other greenwater tank read almost no ammonia. I'm guessing the greenwater was sustaining itself with P by recycling die off or maybe from the tap water but there wasn't enough to use the extra ammonia I was adding.

So you can definitely get away with not using PK. But you'd be growing a less dense culture (which might suite your needs just fine) and you might have to watch the ammonia level.

 

On 3/10/2023 at 5:21 AM, TOtrees said:
On 2/26/2023 at 11:41 PM, modified lung said:

water

Tank water? Or are you seeding the green water cultures from prior batches?

I seed from prior batches now but my original greenwater was from tank water in a jar with ramshorn snails. I had to sanitize the culture tank and run the water through a fine filter sock to keep the protists, rotifers, and seed shrimp out. 

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On 2/26/2023 at 11:41 PM, modified lung said:

I usually  add 1 mL of the ammonia and 0.25 mL of the PK fert per gallon of water at a time which makes about 5 ppm of NH3 and PO4. I do that a few times until the greenwater gets nice and dark

Do have any thoughts about one species of algae over another for green water.  I’m not sure what’s growing on the side of my containers but the free floating algae appears to be Scenedesmus Sp.  
 

I was thinking about ordering some Chlorella vulgaris, but I’m not sure if it makes any difference.

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On 3/12/2023 at 12:00 PM, memorywrangler said:

Do have any thoughts about one species of algae over another for green water.  I’m not sure what’s growing on the side of my containers but the free floating algae appears to be Scenedesmus Sp.  
 

I was thinking about ordering some Chlorella vulgaris, but I’m not sure if it makes any difference.

I actually tested this out and a diet of mixed species of microalgae seems to be a little better and also way less effort then keeping and feeding a pure single species of microalgae. Most things need a varied diet so it makes sense.

I was growing some small rotifers for a while that couldn't eat anything much larger than a Chlorella cell so I had to keep a pure enough culture on hand.

Usually I just let whatever shows up grow but sometimes my cultures get contaminated with a filamentous microalgae that nothing can eat. I think this has happened twice in the last few years. You wouldn't know it unless you have a microscope or your Daphnia/Moina never seem to clear out the water.PXL_20220819_012109074.jpg.cf803149def8cfea6d459729578db4d4.jpg

I can't get rid of this stuff unless I dump my culture and sanitize everything. I keep spirulina powder on hand in case this happens but I wouldn't have to worry about it if I put in effort to keep a more pure culture.

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On 2/26/2023 at 11:41 PM, modified lung said:

I usually  add 1 mL of the ammonia and 0.25 mL of the PK fert per gallon of water at a time which makes about 5 ppm of NH3 and PO4. I do that a few times until the greenwater gets nice and dark.

So I've been trying this an I can't get it to work. 

  1. I have a quart jar with aeration.
  2. I've added ammonia and MorBloom to dechlorinated tap water to achieve NH3=8ppm, P=4ppm, k=20ppm
  3. I've filter about 4oz of my existing culture through paper towel so it's mostly just Scenedesmus
  4. Add the result pale green water to my jar
  5. My photo period is 8 hours/day
  6. and...nothing -- it's starts out very slightly green and clears up in a day or so. 

I find no sign of the algae (or anything else alive) under a microscope.  I don't get some fluffy white something (see photo) -- maybe precipitate, maybe dead something.  There are no visible cells in the fluffy stuff (alive or dead).

Any ideas?  Is my ammonia too high?

 

image.jpeg.ce16c56d7e1e0f8fce5ac11b41b3663a.jpeg

Edited by memorywrangler
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@memorywrangler Weird, I've never seen fluffy white stuff like that in my cultures. It looks like bacteria floc. Any water cloudiness? Not sure where so much bacteria would come from though. Could there be something on or in the paper towel that's feeding the bacteria? I've used coffee filter paper with good results.  Try that if you have some.

Ammonia is fine. You can go way higher if you can wait for it all to all be used up. That's more potassium than I would expect. Is that all from the Morbloom or is your water high in K? Or maybe I did the math wrong.

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On 3/19/2023 at 4:02 PM, modified lung said:

Is that all from the Morbloom or is your water high in K

I'd never measured my tap water, but it turns out it has K=10ppm.   Useful to know.

There is no cloudiness.

My report about the lack of visible cells in the floc was from an earlier trial with less algae.  I looked again with the current batch, and there's some bleached out algae in the floc.

Am I right to think that growing green water in this way should be relatively easy?  How long does it take it to darken up noticeably?

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How are you harvesting out of the jug? I may have to start up some daphnia myself. I haven't really played with them since I moved to this house and I have no chlorine in my water. It seems a shame to not try and work on it

 

 

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On 3/19/2023 at 4:53 PM, memorywrangler said:

and there's some bleached out algae in the floc.

I had bleached out algae when trying to use water straight from the tap. I'm not sure I've tried dechlorinator with greenwater. Dechlorinator can kill Daphnia so I avoid it. Maybe that's the cause? There's so little chlorine in my tap I just have to let the water sit over night.

On 3/19/2023 at 4:53 PM, memorywrangler said:

Am I right to think that growing green water in this way should be relatively easy?  How long does it take it to darken up noticeably?

One thing I figured out is growing greenwater is way more complicated than you'd think.

The tank on the left just started recovering from a huge protist contamination that cleared out almost all the microalgae (pic taken January 25th):PXL_20230126_025918331_exported_1674702461550.jpg.069dde0719db2c6f432ba4eb3839d14d.jpg

All the protists died and the microalgae came back (Feb 8th):PXL_20230209_032130921.jpg.4069d72780f1dc47626ab47af61d8841.jpg

(Feb 16th):PXL_20230217_021901151.jpg.901e0d12d6d49b2d1ed6912ff741a099.jpg

The black line relates to the greenwater concentration: Screenshot_20230319-1908122.png.d895a4e0fcc4b0f5946485d13db78f66.png

Also try putting some fresh grass from your yard into the culture. Idk why but it seems to kick start greenwater better than most other things. I put ramshorn snails in there sometimes too.

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On 3/19/2023 at 5:33 PM, Cory said:

How are you harvesting out of the jug? 

 

 

I should add that my original plan was to use the spigot to harvest.  That works ok if I drain a lot of the volume (like 30%), but draining small amounts of water doesn't yield many moina.  If you watch, you can see them swimming against the current and away from the spigot.

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I've had really good results using alfalfa as a primary feed for moina cultures. Typically start with 3/4 grams (don't really measure anymore) in a mesh bag which I let soak and break down for about 4 days before adding my starter culture, the moina feed on the bacteria that are eating the decomposing plant matter. Makes for a really easy culture and I've used this with and without extra light on my culture containers. 

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On 3/19/2023 at 7:10 PM, modified lung said:

I'm not sure I've tried dechlorinator with greenwater. Dechlorinator can kill Daphnia so I avoid it. Maybe that's the cause?

It seems like this might have been it.  I tried again last night with RODI water and already I see substantial algae growth and no floccing.  Of course it's all on the sides of the container instead of in the water column.  Still, it's encouraging to know I can grow some kind of algae.

On the other hand, and while I've been trying to get the green water ready to sub-culture from my remaining, previously-healthy moina culture, it crashed...

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The ammonia is all gone -- it went faster than I expected.

How much higher can I safely go with ammonia, do you think?  Is more K and P ok too?  It'd be nice to not have to feed the green water that often.

 

On 3/19/2023 at 4:02 PM, modified lung said:

Ammonia is fine. You can go way higher if you can wait for it all to all be used up

 

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On 3/26/2023 at 2:37 PM, memorywrangler said:

The ammonia is all gone -- it went faster than I expected.

How much higher can I safely go with ammonia, do you think? 

Biofuel producers will add 400ppm ammonia and even higher to grow their greenwater. Just add as much as you're comfortable with keeping in mind that if you're feeding the greenwater to your Moina, the extra ammonia in the greenwater will be added (although diluted) to the Moina culture as well. I don't remember their threshold (I wanna say it's 4ppm) but Moina don't seem terribly sensitive to ammonia.

On 3/26/2023 at 2:37 PM, memorywrangler said:

Is more K and P ok too?  It'd be nice to not have to feed the green water that often.

There's a paper somewhere that talks about high K causing more reproduction in Daphnia. I've never done a K test so I have no idea how high mine get or if it can crash everything. I've had adding Seachem Replenish both kill and cause a huge growth spurt over night in different greenwater cultures. Replenish has Ca, Mg, K, Na, and Cl. So too much of something can be bad. i just don't know what that is. 

I used to think P needed to be at least half of N but I'm not sure that's true anymore. Something I've been noticing is if P is higher or around the same level as N, there's definitely a growth delay when you first start a new culture (maybe a week, give or take). But when P is higher the greenwater seems to die off much, much slower if N runs out which makes keeping your greenwater alive a lot easier.

But then there are reports of greenwater having more nutritional value if P is kept low. Idk if it's higher enough where it really matters though especially if more P = easier.

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You can feed them first bites fry food or yeast

Also I dont even use green water at all and they do fine. I have a couple cultures in gallon jars that I feed with first bites and I also culture them right in the tank with my freshwater pipefish, those don’t get fed anything special.

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  • 4 months later...
On 3/11/2023 at 1:39 PM, modified lung said:

I had to sanitize the culture tank and run the water through a fine filter sock to keep the protists, rotifers, and seed shrimp out. 

Hi, my family will be attempting to culture both moina and daphnia pulex. Is the reason for sanitizing and filtering because those other organisms might eat or compete with the moina?

Can I simplify and culture both moina and pulex together in the same tank?

Edited by HelplessNewbie
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It's been a while, and my moina project has become kind of a disaster.   A few things have happened:

  1. My efforts to culture green water have failed.  I stopped short of ordering a chlorella culture.
  2. The exception to #1 is in containers where my moina live.  The water is pea-soup green, but the moina have not been doing well.  Their numbers will spike after a big water change and then quickly crash.  They don't seem to eat the green water.
  3. I have a scud infestation, and I think they might be eating the eggs?  Getting rid of the scuds and keeping them a way is a big challenge because I have scuds everywhere.  It's mostly on purpose, but they are in the water storage buckets I use to supply all my tanks.

At this point, I'm either going to batch culture them in clean water (grow out, feed them powdered food, harvest until the crash, tear down, and repeat), or reclaim the space in my "fish room" and just hatch brine shrimp continually.

It's been pretty frustrating.

On 8/14/2023 at 9:49 AM, HelplessNewbie said:

Hi, my family will be attempting to culture both moina and daphnia pulex. Is the reason for sanitizing and filtering because those other organisms might eat or compete with the moina?

Can I simplify and culture both moina and pulex together in the same tank?

At the time, I thought the cyclops would eat the moina, but I think the variety of cyclops I have are way too small for that.  Now, it's a big free for all in there and that was working for a while, but as I said in my previous post it's been a disaster lately.

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