# hungry daphnia



## Fishfur (Mar 4, 2012)

Got more of these rather cute little critters from Igor at the BBQ. I've set them up in their own tank now, and I added some tank water from one of the aquariums with plenty of snails, which Jackson swears by for keeping them happy. I'm even giving them some snails of their own.

I didn't feed them yesterday, wanted to let them settle down some. This morning I poured in some greenwater for them, enough to turn the water to the palest of pale greens. I was hoping it would last them awhile, as I will be away for some days after today. 

I just now discovered they've already cleared the water to crystal. So they must have been pretty hungry. There are not too many of them, so they must have been feeding heavily to clear even a 2.5 G tank so quickly. So I poured in a lot more greenwater, so it looks like pea soup. Hopefully this will last them longer.

Maybe this time they'll reproduce and keep going on.


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## shawn84 (Mar 12, 2013)

They will destroy the green water rather quick and youll get an explosion of daphnia in no time.


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## Fishfur (Mar 4, 2012)

They've now survived ten days without feeding at all, because I was away. Tank walls are a bit green.. don't think I mind that, but there were live daphnia for sure. More greenwater and I'll give them yeast today as well.


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## bettaforu (Sep 6, 2009)

Karen throw in an algae wafer and watch them attack that! That's how I catch mine I put an algae wafer in a small bottle and once they are all happily inside eating I just pull the bottle up quick with a nice snack for my fishies inside


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## dock (Sep 6, 2011)

Fishfur said:


> They've now survived ten days without feeding at all, because I was away. Tank walls are a bit green.. don't think I mind that, but there were live daphnia for sure. More greenwater and I'll give them yeast today as well.


It's good to know daphnia can live on greenwater for a few days, do most of them survive or just a few?

How other folks feed their daphnia when they're away for vacation? There is no such thing called auto yeast feeder.


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## shawn84 (Mar 12, 2013)

Daphnia feed on green water. So depend on how concentrated your green water is you don't have to feed them for weeks. I keep them in a 5 gallon tank and it will take me a month before it is clear again. That being said I do keep a light source on top of the tank with 16 hrs a day and a sponge filter.


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## Shrimp Daddy (Mar 30, 2013)

They like cucumbers too.


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## Fishfur (Mar 4, 2012)

Cukes ? how does a filter feeding organism eat a cuke ? Not arguing, just wondering is all. I was fairly amazed that any of mine survived ten days without feeding. Every scrap of greenwater and yeast I gave them up to the day I left was devoured within hours, leaving the water like crystal. 

Just before I left, I poured in a fairly concentrated dose of yeast. Turned the water quite milky.. I hoped that would last them at least a day or two. No idea how long it might have lasted, but the tank walls were for sure turning green when I got home. 

They appear to have cleaned up the greenwater I gave them when I did get home as well. So far as I understand, they are not capable of eating algae off tank walls, like a shrimp can, because they are filter feeders.

I do wonder if the water contains enough infusoria that it might have helped keep them going. Without a microscope to check, hard to tell about that. Hopefully now they'll start to reproduce. 

The tank they are in is only a 2.5.. they are few enough that a larger tank would make it much harder for them to find food, or else I'd have to saturate a larger tank with a lot of greenwater to make it dense enough for them to find enough to eat.

Still don't see how they can eat cucumber.. unless a slice of it is producing an infusoria bloom they can feed on. I can see them being attracted to an algae wafer, it must smell right to them, but it would have to dissolve into quite fine particles for them to eat any. 

Single cell algaes such as I have in my greenwater are no more than 4 microns or so in size. I don't know what would be a maximum size for a daphnia's food item, but it can't be a great deal larger than the algae, I'd think. If I'm wrong on that, do please educate me.


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## dock (Sep 6, 2011)

Fish can live without food for a week, and I wonder if the same goes for daphnia. How much green water that you use that lasts for a month without killing them? Any guidelines? I think I might pickup some green water, does LFS sell green water in small amount? 

I've got cucumber at home, how do I prepare it? Just a small slice with or without skin? Do you remove it after a few days or just leave it in?
I heard potato is good too.


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## Fishfur (Mar 4, 2012)

While greenwater is sold by some LFSs, unfortunately, it's for feeding corals and is cultured in salt water only. The salt content in the water would very probably kill fresh water daphnia. Straining algae cells from salt water effectively is impractical due to the tiny size of the cells.

I don't know any store that carries fresh water cultured algae. The main use for it is feeding corals, so only salt water cultures are readily available. I've not a clue what amount of greenwater would keep a given number of daphnia for a given length of time. For one, how would you count the daphnia to know how many are consuming the algae ? Two, how would you count the cells in any given amount of algae culture to know how much was consumed ? Weighing might be one way, but a lot of work.

The only visible sign you have to go on when you feed greenwater or yeast water is how long it takes for the water to clear after you feed. It turns cloudy when first added, but as the food is consumed, the clouding effect gradually diminishes 'til the water is clear; one reason daphnia are so very effective at clearing greenwater bloom in a tank.

You should realize that daphnia do not 'hunt' for food, like fish or shrimp. Instead, they continuously take in and expel water, sifting out anything they can use in the process. In other words, filter feeding; similar to fan shrimp or clams. Shrimp have the advantage in that they can move to other places or even bottom feed. Clams are able to move, but not easily, and bottom feeding is not an option, for clams or for daphnia either. Sure, daphnia can move, but even a square inch of volume is a huge space to something so tiny. Thus, the denser their food source, the better their chances to find enough.

One very short term alternative to cultured single cell algae could be bottled liquid Phytoplankton sold for feeding corals. Kent makes one; there are others too. No salt in it and I use it sometimes for my fan shrimp and clam, mainly for dietary variety. It's extremely expensive.

Yeast is the best alternative.[ I wonder if fan shrimp would like yeast ?] Baker's yeast well dissolved in water, [perhaps with a 1/2 or 1/4 tsp. of sugar for the yeast to feed on for the first ten minutes while they dissolve], makes a good substitute. When fish eat daphnia, they eat what those daphnia consumed. Rather like gut loading insects for reptiles or herps, feeding daphnia nutritious food means they have more to offer the fish who consume them. They are mostly shell, after all. Their gut content is quite tiny, but they're eaten in huge numbers, so it adds up. In terms of nutrient content, algae is very nutritious, yeast, reasonably so. As SwimmyD learned, fresh yeast, if you can find it, is VERY eagerly taken by daphnia. The drawback is a very short shelf life. Once it starts to deteriorate, or mould, it's not safe, so toss it. Keep in the fridge, well wrapped ! It dries easily [ dead if dry ] and at room temp it will go off so quickly it's not worth buying.

Btw, I could have some green water ready to sell in a week or two, if anyone wants some and then you can keep it going yourself. I culture from pure species discs I get from Reef Crew. Nannochloropsus, aka, Japanese chlorella, is the only commercially available single cell algae I am aware of that will grow in either fresh or salt water.

You need very high light and small amounts of ferts to culture it. I prefer the special formula, Guillard, that Reef Crew sells specifically for growing algae. Some folks use ordinary ferts.. plenty of info online on this. You need light; either an unobstructed,very sunny window, [ pretty much summer's only], or better, 65-6700 K lights, [spiral type works] as close to the bottles as possible, running 18 hours daily. My cultures get 14 - 16 hours, as I use my light garden for the light source. The shorter timing might slow growth a bit, but is not a problem.

Or try 'homemade' green water. Lots of info online. Use a nice clean jar, fill with tank water taken from the filter outflow, left in a very sunny window. It will often turn to greenwater. I keep a bit of the nuisance algaes I find in my tanks inside my 'home made' green water jar, and a bunch of rocks which also grow algae, and when the rocks are nicely green, I give them to the Otos and shrimp. When the rocks are cleaned off, I toss 'em back in the jar. The solid algae, on rocks or floating, has so far kept this culture smell free. Moss might do the same. I also add ferts to the homemade, same as I use for the pure cultures.

It takes time for a culture to become dense enough to use. Home made takes longer than a pure culture. Home made might also turn into an infusoria culture instead. Don't allow any snails in the jar, their waste might promote infusorial growth. Infusoria are not necessarily bad, daphnia can eat them, but your jar might get rather smelly. This might make you unpopular with other family members , if you haven't anywhere to keep it out of 'whiff' distance.

The way to tell if it is dense enough to feed is to place one hand behind the jar and look through the liquid in good light. When your hand is barely visible or invisible, it's dense enough to feed. Divide it and use half to propagate another culture, so you don't run out. You do the same with a commercial culture.

I don't doubt daphnia can live for some period of time without food. Most creatures can survive varying lengths of time, either without their usual food, or with none at all, barring those few with very high metabolic rates, such as shrews. How long daphnia can go with zero food intake would be, I'd think, a guess at best. Anybody know reliable stats' on this subject ? Want to try some experiments maybe ?

Daphnia can live on bacteria and infusoria, which we generally don't see unless their numbers are sky high, so it might appear they have no food, when they actually do have some. I've wondered if it would be useful to keep leaf litter on the tank bottom, such as oak or almond leaves, to encourage the growth of infusoria as a secondary food source ? I might try that when I have enough daphnia for a second tank.

I too would like to know how one feeds things like cucumber to filter feeders.


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## Shrimp Daddy (Mar 30, 2013)

dock said:


> Fish can live without food for a week, and I wonder if the same goes for daphnia. How much green water that you use that lasts for a month without killing them? Any guidelines? I think I might pickup some green water, does LFS sell green water in small amount?
> 
> I've got cucumber at home, how do I prepare it? Just a small slice with or without skin? Do you remove it after a few days or just leave it in?
> I heard potato is good too.


Put slice of cuke in jar with tank water. Put hy window an you will have green water.

My shrimp love sweet potato so can't see why daphnia won't.


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## Fishfur (Mar 4, 2012)

So you're not really feeding them cucumber, you're using cuke slices to start an infusoria or greenwater culture, and they feed on that. That makes much more sense.

Sweet potato likely would work, regular potatoes work for this as well. But you will get faster results using tank water with the cuke or potato slice. I don't use this method because it can result in a pretty smelly jar sometimes.


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## Fishfur (Mar 4, 2012)

Despite feeding them greenwater, I'm not seeing much reproduction with my daphnia. 

In fact, since I got home, I'm seeing fewer and fewer daphnia altogether.. I am not sure what I might be doing wrong. They have a sponge filter running slowly in a 2.5 G tank. 

I wonder if the recent warm temperatures are part of the problem ? It just might be too warm where I've got that tank at the moment. I am seeing lots of what I thought were moulted shells on the bottom, but now I think a good portion of them are deceased daphnia.

So much for the benign neglect theory of daphnia keeping :-(.


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## Jackson (Jan 30, 2009)

I wouldn't use a sponge filter just an air stone. 

I only feed mine yeast. I have them in a room about 30c right now and they're fine.


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## LTPGuy (Aug 8, 2012)

Fishfur said:


> Despite feeding them greenwater, I'm not seeing much reproduction with my daphnia.
> :-(.


I have similar observation with my batch. However, I am using greenwater as a supplement rather than for bulk feeding. I use dry yeast which is cheap, easy, and effective.

I observe the daphnia form a mad swirling cloud around the light source when I add greenwater or yeast mix. So it's clear that they are feeding.

When I withheld the yeast, the daphnia take on a light greenish tint, and the population growth and growth rate seems to be slow or non-existent.

With yeast, the daphnia take on a darker (brownish to dark brown) colour, and the population growth is very evident.


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## matti2uude (Jan 10, 2009)

I have mine in a 2.5 gal with nothing. They are reproducing ok. I feed them little pieces of any kind of veggie food I'm using at the time. Mine seem to be a pinkish colour.


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## Fishfur (Mar 4, 2012)

I can only see a very few live daphnia now. The sponge filter is running very, very slowly. I put it in because I knew I'd be away for a week or more and was concerned because I would not be around to add or change water.

I have fed them since I got home, and they have not cleared the water yet, even though when I got them, at the BBQ, they were clearing a good dose of greenwater in only a couple of hours. 

If the heat is not the cause, I wonder what is, because they appear to be dying off. Most discouraging.


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