# Daphnia as bio-control of algae



## gmartins (12 Jun 2011)

Hi,

After seeing some tiny animals around my tank, which I am pretty much certain they are Daphnia, started thinking about this.

If you have fish you can forget it as they will promptly eat them up. However, many of us are keeping fishless tanks (some shrimps maybe). I know that some species of Daphnia can regulate the amount of plankton in natural lakes. They do not seem to negatively affect plants. So my question is: would Daphnia be a good addition to planted fishless tanks as a means of controlling algae, or at least some types of algae? I'm thinking for instance of green water and maybe others.

does any one has any experience with this? Looking forward to hear your thoughts about this.

GM


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## ceg4048 (13 Jun 2011)

Hi,
    Daphnia will feed on green water algae and that's about it. Since these are free floating organisms the daphnia will gobble them up albeit slowly. These are not much use for any other algal types though. If you have green water algae then a UV will make short work of it, so it's not really efficient to use daphnia.

In any case, depending on animals is not the best path to controlling blooms. Optimizing plant health is the best mind set in the long term.

Cheers,


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## gmartins (13 Jun 2011)

Hi Ceg,

I have no green water. Was just thinking about it. There is quite a large body of literature on how efficient daphnia can be. In fact, ecosystems can be disrupted if daphnia are all eaten for isntance by the introduction of daphnia-eating fish.



			
				ceg4048 said:
			
		

> Hi,
> In any case, depending on animals is not the best path to controlling blooms. Optimizing plant health is the best mind set in the long term.



Absolutely. I just thought they could be used along with otos, amanos or nerite snails as part of the "cleaning" team.

cheers,

GM


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## dw1305 (13 Jun 2011)

Hi all,


> I have no green water. Was just thinking about it. There is quite a large body of literature on how efficient daphnia can be.


 I usually seed my tanks with a few _Daphnia_ during the set up period, they are extremely efficient at hoovering up any suspended particles of the right size (you can feed them with either Yeast, gram flour or paprika powder if you are culturing them), and will rapidly clear a pond if their are no fish present.

cheers Darrel


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## ghostsword (13 Jun 2011)

I had a 20L shallow tank on the garden and it was very green. I added some daphnia to it, and two weeks after it is clear. Not even algae on the glass, and it is on full sun, has ferts from the main tank drop into it, and it is now my moss farm. 

Daphnia are very good.  

The only issue is that mine are not small anymore, they are large round brownish animals, that the fish love to eat.


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## Brenmuk (13 Jun 2011)

I remember back in the 90's when I used to read PFK they looked at a product to clear ponds of green water algae. It was a clear canister that you pumped pond water through containing daphnia. The idea was that the daphnia ate the green algae and were protected from the fish in the canister.


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## dw1305 (14 Jun 2011)

Hi all,


> The idea was that the daphnia ate the green algae and were protected from the fish in the canister.


There is a large body of scientific work which looked at the feedback cycle of:

 "loss of macrophyte (higher plants) refuges > loss of _Daphnia_ (due to increased fish predation) > growth of "green water" algae > loss of water clarity >lack of light to support submerged macrophytes > followed by increased predationon _Daphnia_ etc."

This is what happened in the Norfolk Broads where agricultural run-off and increased phosphorus levels (from sewage and washing powders (the "optical brighteners" were P based)) combined with the turbulence of increased boat traffic led to algal blooms,  which reduced light penetration killed of the submerged macrophytes, which died leading to increased predation of the _Daphnia_, which led to thicker algal blooms etc. The mechanism is more complex than just the physical shelter offered by the plants (there are nutrient effects), but fish free refuges work by physically protecting the zooplankton from predation. 

Details here: <http://books.google.co.uk/books?id=...ook_result&ct=result&resnum=1&ved=0CB0Q6AEwAA>

cheers Darrel


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## gmartins (14 Jun 2011)

Yep there are millions of scientific papers showing how important Daphnia can be in freshwater ecosystems.

I also remember reading an experiment (cannot find the article) where Daphnia were able to control green water even in nutrient-enriched waters. They are therefore a key species in these freshwater ecosystems.

So I suppose my thoughts were right. They can be used in fishless tanks to promote water clarity and make a good addition to the remainder of the "cleaning team".

As of curiosity, I can now see some small animals hovering around my fishless tank. Shrimps do not bother with them. At naked eye they resemble the general form of rotiferers but I cannot tell for sure. Probably came with some plants. Will try to collect some and have a look at the microscope.

G


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## gmartins (14 Jun 2011)

Yep there are millions of scientific papers showing how important Daphnia can be in freshwater ecosystems.

I also remember reading an experiment (cannot find the article) where Daphnia were able to control green water even in nutrient-enriched waters. They are therefore a key species in these freshwater ecosystems.

So I suppose my thoughts were right. They can be used in fishless tanks to promote water clarity and make a good addition to the remainder of the "cleaning team".

As of curiosity, I can now see some small animals hovering around my fishless tank. Shrimps do not bother with them. At naked eye they resemble the general form of rotiferers but I cannot tell for sure. Probably came with some plants. Will try to collect some and have a look at the microscope.

GM


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## dw1305 (15 Jun 2011)

Hi all,


> At naked eye they resemble the general form of rotiferers but I cannot tell for sure


 They may well be Rotifers, they are very common in both the biofilm on plants, wood etc and in filter sponges. _Keratella_ spp. are common swimming ones.

If any-one wants to admire Rotifers in their full beauty, have a look here: <http://www.microscopy-uk.org.uk/mag/wimsmall/rotidr.html>, <http://www.microscopy-uk.org.uk/mag/artnov99/rotih.html> & <http://www.microscopy-uk.org.uk/mag/wimsmall/extra/rotif.html>. They are some of the strangest organisms.

This is a colonial form - _Conochilus_






cheers Darrel


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## ghostsword (15 Jun 2011)

Daphnia are really cool to eat algae.

This is the acrylic tank they are on, on full sun, with water from the main tank, so it has ferts, lots of light, no filter, but no algae either. 


Untitled by GHOSTSWORD, on Flickr


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