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Adventures in Daphnia


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I have been experimenting with Daphnia in different containers and feeding different recipes this summer. To jump to the end my conclusions are basically keep them cool and keep it simple. Nothing really new or profound there for experienced live food aquarists. I am on a live food for aquariums group on FB which gave a lot of good advice on recipes in particular. The consensus in that group was primarily to feed green water or there are some very specific precipices involving spirulina and different organic flours that work. The issue is the successful recipes are more complex (meaning 4-6 ingredients) and you have to be very precise and consistent in your feeding and cleaning. My own experiments with these recipes has born this out.

With green water you can be much more imprecise and the chance of crashing your culture is much lower than with the other recipes. Especially yeast which is the easiest way to crash your culture. My most successful culture was in a 15g outdoor container pond that only had frogbit whose shade helped cool the water. The pond had gone super green water when I put the starter culture in and they exploded. I was feeding them to my goldfish almost everyday. Then of course I put in an Endler trio and eventually they and their progeny ate all the Daphnia. However that took a long time and was good for them so still win-win.

I don't have room for more containers in our very small backyard here in Brooklyn so now I am raising a couple of batches in the basement and feeding only green water. In another experiment I have taken two 1 gallon glass jars, added rigid airline tubes for aeration, filled them with green water (grown outside with grass clippings) and added just a few Daphnia to only one jar. Below is a photo of the two jars after a week. I put a sheet of white paper behind them to help see the color. In real life the color is greener than this BUT the contrast in lightness of color is accurate. 

Interestingly the darker color jar on the right is the one with Daphnia who have now reproduced. The lighter color jar on the left has no Daphnia. This may be due in part to the jar with no Daphnia not having enough light to fuel algae growth, it may be there were fewer nutrients in the water to start or something else. I am now going to try adding EasyGreen to the empty jar to see if that helps grow some more free floating algae.

I am also going to rig up another setup using 2L bottles on the SF Bay Brine Shrimp Hatchery Kits (these from the Coop: https://www.aquariumcoop.com/products/brine-shrimp-hatchery-kit) with extra light to see how that does. In one bottle I will add regular green water and in the other I am going to try a freshwater phytoplankton culture, probably Chlorella, to see how those do. I will also feed these.

More to come including an idea for a drip feed system I am working on.


My 15g container on top that grew the Daphnia so well and my 40g goldfish container pond below.




Edited by pedrofisk
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  • 1 month later...

It's been interesting. For making green water the successful recipe is Easy Green, cut grass and always leave 20-30% of the old water when refilling. I am using 1 gallon jars and that matches well to my 6 gallon kritter keeper I am raising them in. Using green water over any other food is 100% the way to go.

The next most important thing is not to let the population get too big as it is easy to crash the culture with Nitrate buildup or they eat the green water so fast too many starve before you notice and they crash. I have also found I am not successful in anything less than 5 gallons. That one has me a little nervous as I don't have a second backup culture working right now. I am also using 12 hours of light which I read they like in a scientific paper.

My next big challenge is figuring out a successful formula for green water indoors as the weather inches closer to freezing at night. I have not hooked up the drip system yet with all the chaos of life/works/kids/remote learning/starting fish room renovation etc but I will hopefully soon.

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