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Daphnia cultures and more
Wow Mach, you must indeed now live at a high altitude in Hawaii to need to
paint your daphnia tanks black! We raise what is probably D. pulex here and
(in northern Illinois) worry about too much heat and not enough oxygen. On
the other hand Adrian, if you live on the Mexican Central Plateau that may
be an issue for you too.
I would really echo George's suggestion that you look in local temporary
ponds for a starter culture. It would be better, by the way, to look for
them in a pond or puddle with no fishes in them. While it may be not a major
issue, pulling them from waters without fish or too many other creatures
makes them less likely to carry parasites which might harm your fishes.
If you have space, set up two or more cultures. Most food cultures will
crash from time to time. It happens to us all. I think I took and
distributed ten starters in the last week or so at local clubs and exhorted
everyone to start two cultures. Otherwise they have to drive to my place for
Yeast is a good food, but must be dissolved in warm water which is mixed
before adding it to the tank. Only very lightly tint the water. I find it
easy to be clumsy and overfeed yeast. The daphnia suffocate. Needham et al
(Laboratory Culture of Invertebrate Animals) suggest that the two best foods
for indoor cultures are either yeast or greenwater. Greenwater is much
safer, in that it will live and reproduce forever (or until consumed) in a
Indoor cultures should have an airline. A modest flow from a hard airline
tube is better than using a fine airstone - the fine bubbles may float the
I would defer to George in 99.9% of what he would say on most any aquaristic
issue, but do believe that bigger containers are better. They are more
stable in terms of water temperature, oxygen and water quality. A little
depth of 50 or more cm (so long as children are not endangered) is
An empty outdoor culture here may be started with a half bag of the
composted cattle manure available at garden centers. That is already pretty
benign as manures go and must have sat for quite a time.
My outdoor cultures are under trees. Leaves are always falling in and help
fuel it. Too many leaves and they need to be taken out. Hardware cloth - or
an old stick - does the trick. Pondsnails from a fishtank help the
decomposition process along.
Added greenwater accelerates growth. Adding it with water changes is useful
and encourages the often neglected water changes. If rainstorms are
forcasted, drain some of the water out of the containers outside.
Once in a while we pull some grasses and dandelions from the edges of the
yard and garden and place them in a bucket to ferment for a while. A small
jar of that broth added is useful. Don't feed too much or the water can
The dandelion soup is a great draw for mosquitoes if left long in the sun,
so plan accordingly. The mossie eggs look like little pieces of charcoal
scraped by a fingernail and bob around on the surface of the bucket. They
are easily skimmed off and dropped in fry tanks as a first food for anything
that feeds on the surface. In some places there are not only ethical, but
legal issues which arise if we are sloppy in harvesting them.
In the case of a grass broth which grows mosquitoes, buckets are in this
case the best choice because they can be drained through a fine mesh net
into another bucket. Be careful to feed them so that all of the fish consume
all of the biggers ones rapidly. (My bride still thinks that that one nasty
night in the house, someone must have left a door open.)
Sometimes a daphnia culture will pick up more. I am assuming they blew in
as cysts from a nearby wet land, but we now have cyclops and seed shrimp out
Sometimes bloodworms and glassworms show up as well. Their parents are gnats
who fly in and lay eggs. They are great livefoods. The bloodworms, whose
eggs look like masses of mucus on the barrel sides, are vegetarians and do
well on rotting leaves. The glassworms are enthusiastic predators with a
fondness for mosquito larvae, so be careful not to put them with small fry.
In early spring a blanket weed algae blooms. Shortly thereafter the seed
shrimp hatch, bloom and consumer the blanketweed.
The eggs of all of those little crustaceans can over-winter or over-summer
dry. So if the container leaks (or in the case of one of ours, freezes and
bursts), shovel the dried material in the bottom of what remains to a new
container and add water. Most of the time, there will be a new daphnia
bloom. Daphnia eggs (you will see them from time to time on the backs of
females) are little black specks (quite flat actually) which are impossible
to sort out of dirt.
If you harvest about half of that bloom at a time, you may keep it going
quite a while. Harvesting is something of an art form. If you over harvest
and production drops or you under harvest and everything dies off - you are
not alone! Crashed cultures will usually come back.
Keeping the cultures under trees keep them from getting too warm. It also
cuts down on reflecting the sun. Those reflections can attract flying bugs
(water beetles, backswimmers, water skaters, damselflies, dragnonflies...)
which either settle in or lay their eggs. You will know when they have
arrived by the abrupt decline of the culture. Unless you have large cichlids
protecting eggs masses, the best thing to do with the culture is to save a
daphnia starter, dig a big hole next to it, dump the container into the hole
and fill it the hole up as soon as the water has mostly drained into the
If anyone is interested, I have a couple of slides of the daphnia tubs.
There is a scanner at work which supposedly scans slides. It would be an
excuse (after work hours of course) to try the scanner out and post a jpeg.
All the best!