Re: NANFA-- Spring must be here in Indianapolis

Scott Davis (
Wed, 7 Apr 2004 16:23:57 -0500

>Would it be possible to prevent the freeze over and keep
> Daphnia going over the winter? I do know they are day length sensitive
> and may start producing males, resting eggs, etc. It doesn't happen here,
> but I was just wondering....

Hey Mach!

I'll get over my Moina envy in a bit.

"My" Daphnia (pulex? magna? adequate to the task...) has done pretty good
under the ice in mild winters in Northern Illinois. Tried keeping them in a
leftover plexiglass display case (among other containers). That was pretty
ill advised as demonstrated by events a year later, however that mild year
one could see the daphnia boogying all winter long.

Was able to flip a three inch ice cap off of one of those half whiskey
barrels and get a wonderful harvest late one December. Several of those
containers have been in business for some years. A lot of the leaves are
lifted out in the fall with 1/2 inch hardware cloth. If enough are left to
fuel the culture but not smother it, those daphnia seem quite, maybe even
more productive in cold weather. Less food seems to be needed for metabolism
and can be used for reproduction and growth. A little extra green water from
time to time can do wonderful things.

By the way, a fishhead friend suggested using cheap surgical gloves around
that cold water. The ones I had were so cheap they tore too easily, but they
still did a credible job of keeping hands dry and therefore not numb. Next
year will buy slightly better gloves.

Some female Daphnia will be seen carrying resting eggs/cysts but that is
evident in the back up cultures indoors as well. If there is plenty of food,
there will still be lots of young.

Interesting your comment about photoperiods. Even the indoor backups will
have a few cysts in the summer though.

More recently I've become a little gun shy about leaving the outdoor
cultures full. Usually halloween is a good time to have drained them by
3/4ths. Some warm years have seen them productive to New Year's Day - if one
can catch a day with a little warming so the ice cap can be removed.

This last year, my very fallible memory seems to remember a really nasty
cold wave about mid-October. The weather people called it correctly, but it
was a frantic time draining and harvesting from seven vessels and gingerly
carting the old 40 gallon breeder tank into the cool corner of the fishroom.

So yes, try the "regular daphnia." It should be more productive at your
cooler winter temperatures than in the 70s anyway.

You are welcome to a starter of the stuff we've been passing around the CKA
for a couple dozen years. Because it is kept in a shaded area, there have
been few problems with pond predators joining the community. Nais or
something similar, two sizes of Ostracods and a cyclops seem to have
hitch-hiked in (on the whiskers of varmints?) and show up from time to time.

I've had a few bloodworms from the indoor culture flying around the fishroom
all winter long.

If you want just the Daphnia, a little seiving and pickin' can be done.

Whatever species and strain it is, it seems well adapted to Northern
Illinois weather and, if out of the summer sun and fed a little more
greenwater, most years (lately) will keep on chugging right through July and

All the best!

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