The Daphnia came back!

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Oct 14, 2011
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Eastern Canada
For years, I have had a cheap (free) source of highly nutritious fishfood, harvested from my backyard - Daphnia pulex.

Originally, I started out doing what the aquarists of bygone years loved doing - I found a vernal pond with no fish in it, and could take out kilos of live daphnia every Spring. I would freeze it in blocks. By summer, the pools and their inhabitants would be gone.
In time, I set up plastic tubs in a cool, shaded spot with old window screens to keep mosquitoes out, and used green water to feed them. With these wild caught sources, I was able to get about 5 years of returning daphnia cultures every Spring - useful since McMansions were built over the easiest to get to source (I bet those people have damp basements and mosquito bites all summer).
Where I live now is an ancient river delta with sandy soil, and pools don't form easily. I couldn't find Daphnia, so I bought a vial of eggs last year. They did wonderfully, and my fish food buying dropped for 6 months, while my fish breeding shot up.
I overwintered the tubs in a shed with about 12 cm of water, and leaf litter. They froze solid for a few months. I wasn't sure how the bought Daphnia would do, but I just harvested enough to feed half a dozen tanks, and will leave the breeders for a few weeks to build up the population. The eggs survived the winter and I'm back in business!

I harvested today because some mosquito larvae had gotten in, and I wanted them out before they started eating me. My dwarf Cichlids appreciated that.

The species I use, D pulex, like cooler water, and if there is a solid heatwave, will fall back radically in numbers, til it cools again. There are other species suited to other climates, and you have to do some research to choose from the online sellers. I'm in a seaside spot in eastern Canada, where's it's currently in the teens Celsius. Summer days run about 22-23, and we get a fair bit of rain.

The very old fishkeepers where I used to live would go daphnia collecting a couple of times every Spring, as a social outing. They always talked of it as great fun. Now we look at screens and have fewer laughs as a hobby culture, but you can at least get the benefits of what they learned without falling into a creek.
It's a few weeks later, and today, I was able to fill all my tanks with nutritious Daphnia. A few mosquitoes had gotten into one tub, due to a visit by a thirsty gopher. I had to adjust the weight of the cover on that one. The mosquito larvae won't make it to the point of eating human neighbours, as they are going into fishtanks. I save them for the fish I'm trying to breed as they are far more nutritious than Daphnia.

Still, a culture that was inexpensive and returns year after year, and only demands feeding with green water, a tub and a screen is pretty good. They filter the water until they get eaten. They'll slow if it gets hot, but around here, that's a big 'if'.

If I can keep them going at this level, they'll become my main fishfood for the next while. If you have a shaded corner of the backyard, it's really worth trying.

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