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Fwd: Daphnia and...

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UncleScott at prodigy_net wrote:

> Regarding growing daphnia. We have limited space but would like to
> keep this culture going into the winter. I assume you are telling me
> that a larger container (than gallon jars) would produce better
> results. Would a large plastic container in the basement with little
> light work OK?
          Yep. I've always been good at spending other peoples' money
time and now space however, so be forwarned.

         I may have mentioned the case of the Chicago area aquarist with
a 55 tank on a metal stand. That tank, vigorously aerated with airstones
and corner filters (I can't remember what was in them, I would put in
largish gravel to encourage water flow), was his daphnia tank and lit by
the fishroom's ambient light.

         The 35 gallon tank underneath it had some 6" cichlids,no plants
and lots of light and aeration. It looked like St. Patrick's Day on the
Chicago River.

         Every day this particular aquarists would siphon out a gallon
or two or more of water from the top tank. The daphnia was strained out
through a fine mesh net and fed to his 50+ tanks of killies. He then
replaced that water with greenwater from the cichlid tank. His harvest
was very impressive.
         Yes I would think that if the cichlids were sick, whatever
pathogens could be passed on. However they had been in the family some
time and were doing well.
         I mentioned the set-up sometime later to a biologist and he
nodded knowingly. I had thought that to maximize daphnia production that
the supplying containers would have to be greater in volume than the
actual daphnia cultures. Theoretically it takes 10 lbs of euglena/
paramecium/whatever to produce 1 lb of daphnia. His impression was that
the protists in the greenwater multiplied so fast, that given all of the
food, clean water, light and air they needed, that they could reproduce
at a prodigious rate and keep the larger tank of daphnia well supplied
with food.

         That set-up had the daphnia tank in the warmer position though.
I think keeping a growing container/tank/plastic vat on the basement
floor such as you suggest is even better. Daphnia magna, the species we
call (maybe correctly?) our usual strain, actually does better 10-20 or
more degrees F. below room temperature. One December day outside I
pulled a three inch slab of ice off of a half-barrel and got a terrific
harvest along with the numbed digets.

         If the container is on the floor, a light, with only enough
cord to reach over the container (as a safety factor), can be suspended
above it. (Some people are getting GFI outlets for around their fishes
too.) The light will help whatever greenwater beasties are in your
daphnia culture to continue longer and if the daphnia population is
thin, to even green-up that container until the inevitable daphnia

        Daphnia in bloom can be harvested at such a rate as to extend
the bloom. (Like feeding a culture, how much to harvest is something of
an art form.) I like greenwater above all other forms of daphnia food
because the stuff is alive and with minimum care will live without
fouling the tank. The daphnia for their part, are literally swimming in
food and can eat constantly.
        By comparison, when I feed brewer's yeast, I am careful to mix a
little bit in a small jar in warm water. I add only enough to lightly
tint the water and don't feed again until the water clears, because
dying/decaying yeast will suck all the oxygen out of a culture and the
daphnia will perish. Most of the people I know who use yeast keep
several cultures of daphnia going (a good idea anyway) because they know
that sooner or later they are going to overfeed the yeast and skunk a

        I also fairly regularly rinse plastic milk jugs and yogurt
containers into the 30 gallon plus daphnia cultures because the dairy
products add substance for the bacteria or whatever in there to grow on
and in turn be fed upon by the daphnia. (For all I know the daphnia may
be filtering out the dairy products - they can filter out everything
from bacteria to blended pea soup mixes to newly hatched mosquito larvae
to newly hatched baby brine shrimp!) Again though there is the danger of
adding too much milk and fouling the culture.

        You can see why green water is a safer daphnia food. It is
indeed possible to foul and destroy a straight greenwater culture, but
it is much more difficult.

        Should a daphnia culture crash, I often just leave it alone.
Eggs in the mulm will often bring the daphnia back in a couple of weeks.
Assuming it doesn't smell bad, I'll leave a light on a crashed indoor
culture 24 hours a day. The water will green up and often daphnia will
then appear. If they don't appear or you are in a hurry, then seed the
tank from another culture.

        You also mentioned an air line indoors. This, like water
changes, will profoundly increase your yield. I don't think we realize
the effect of the wind outdoors and those backyard cultures (do leave
them under trees or out of the direct sunlight in warmer months) seldom
need any aeration.

                        All the best,


End forwarded message.