# Water Butt and Daphnia



## AlanRR (27 Apr 2019)

Hi

I have a new rain butt that I’m considering using as a source for tank water changes. I live in a fairly rural area of Yorkshire so there isn’t too much pollution but there is frequent rainfall.  I’ve been reading on the forums about using Daphnia as a way to assay the water quality so that I don’t inadvertently harm my shrimp and snails. Will Daphnia grow happily in a dark butt or do I need to leave the lid off for some light? Also do I need to seed the butt with grass or leaf litter prior to adding Daphnia?

Thanks

Alan


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## dw1305 (27 Apr 2019)

Hi all,





AlanRR said:


> Will Daphnia grow happily in a dark butt or do I need to leave the lid off for some light? Also do I need to seed the butt with grass or leaf litter prior to adding Daphnia?


They are happy in the dark, you need some form of food for them, a few dried grass stem work really well as a starter, after that enough moss and leaves etc will come down the down-pipe from the roof. I only get a trickle of _Daphnia_ from the water butts, if I want a lot I use a builder bucket and feed them more.

You may also find that your rain-water is too soft for them, I just use rain-water but it is all limestone here and our rain-water has some carbonate buffering. A hand full of chick grit (or lime-scale from the kettle if you have hard water?).

cheers Darrel


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## AlanRR (27 Apr 2019)

dw1305 said:


> Hi all,They are happy in the dark, you need some form of food for them, a few dried grass stem work really well as a starter, after that enough moss and leaves etc will come down the down-pipe from the roof. I only get a trickle of _Daphnia_ from the water butts, if I want a lot I use a builder bucket and feed them more.
> 
> You may also find that your rain-water is too soft for them, I just use rain-water but it is all limestone here and our rain-water has some carbonate buffering. A hand full of chick grit (or lime-scale from the kettle if you have hard water?).
> 
> cheers Darrel



Thanks Darrel. We have quite a bit of limestone around here (though the clouds seem to be invariably scooting past at 100 miles per hour so I’m not sure how local they are ). Is there a reliable way to assay carbonate hardness without science grade instrumentation or is it not worth the effort? The TDS of the rainwater it is currently around 65uS if that provides any clues. I already have some oyster grit in the filter so could probably just leave it there.

Cheers

Alan


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## TBRO (27 Apr 2019)

They are quite happy in my water butt with a lid (have small children). 

As Darrel says they will need some food, I have some old lumps of bog wood in mine. I’ve started feeding them with a jar of green water a week and the population has boomed. 


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## dw1305 (27 Apr 2019)

Hi all,





AlanRR said:


> The TDS of the rainwater it is currently around 65uS if that provides any clues


About the same as mine. I find it is usually a bit higher in the summer and lower in the winter. I'd see how you get on with the rain-water as it is.

cheers Darrel


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## TBRO (5 May 2019)

Tried taking a photo of my colony today, you can see the wood (old bit of oak root). Water butt is teaming with them at the moment. 


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