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Greenwater and lighting
> I keep a 40 watt incandescent about 5 inches above the surface of the
culture. The daphnia congregate beneath it and are easily harvested.
> It is on for about 12 hours a day.
Bill has several good points. Long hours on a timer and closeness to a
culture are good. There are a couple of provisos to the latter.
I run the lights in my fishroom on timers set to gradually go on one after
another. "Sunset" also is a gradual process.
By the way, livebearer guru James Langhammer, in a much alluded to posting
on his Russian daphnia, recommends leaving at least a small light (kind of a
moon?) on 24/7 over the daphnia so they will not gather in a corner of the
raising container and suffocate.
Especially if you are using your light to grow greenwater in with your
daphnia, you want you light as close to the tank's surface as is possible,
safe and realistic.
Plant people will note that lights closer to a tank don't spill as much of
their out put elsewhere. By the way, on the killie list they have had
several threads recently alluding to lighting. One which especially got my
attention was the consideration of how reflective the light cover/ hood is.
That can make a huge difference in what really gets to the tank. Someone
kidded about using the aluminum foil from potato chip packages (like I need
another excuse to eat potato chips). Wright Huntley, who sometimes also
holds forth on this Digest too, startled some readers by noting that the
reflectivity of those foils might indeed be useful that way.
Notice that Moon uses a major lighting fixture over his culture(s). Over
heating the culture and safety concerns are obvious in his 24" distance.
I imagine if you went to the Actwin site and searched the archives of the
aquarium plant list you would find tons of stuff on reflectors. Check out
Actually you will also find a bunch of additional things on Greenwater in
the archives of this list. Google searches will summarize a bunch of things
from aquatic mailing lists and Digests, including this one.
Obviously you don't want to get water in your light. (Did you ever consider
getting GFIs for outlets near any water and fish stuff?) And you want to be
able to do water changes and what-have you with the daphnia and need space
Raising daphnia, what with the feedings and water changes which will
increase your culture's productivity, (actually 2 or more cultures is
better...) begins to sound a lot like raising fish.
Raising greenwater sounds a lot like raising plants too. Basically you set
up a tank to raise plants - and neglect to put any plants in. Most any
aquarium water already has small numbers of euglena, paramecium and the rest
of the greenwater crowd. Given optimum conditions they should bloom.
It is best to give it some water movement to keep it (the photosynthetic
protists which make up greenwater) from settling out when they bloom and
turn the water green. Use either a solid airline tubing, a box filter
without anything in it or a small power filter without filter medium (you
don't want to filter the greenwater out). Water movement and gas exchange at
the surface are the goals.
If you have several growing, hungry fish to put in that tank, they will
provide the organic nutrients the daphnia will need. For instance I have an
old 40 gallon breeder tank (rescued from the end of a club auction for $4)
on the floor of my fishroom. The greenwater tank is a 20 variously full of
rainbowfish, killies or livebearers. I should do my best to help the fish
Ideally I can remove 3 to 9 gallons of greenwater from the fish tank daily
and feed it to the daphnia. Before doing that, obviously a corresponding
amount of water must be removed from the daphnia tank. If the daphnia are
thriving, those caught (I use run the siphon hose through a very fine sieve
(the Nuovo brine shrimp sieve) are sized through various sized sieves and
fed. If the daphnia culture isn't doing so well, the caught wee beasties are
returned. Having removed that much from the greenwater tank means that a
corresponding amount of seasoned water must be gradually added to that
greenwater tank. Those fish have never complained about the water changes.
Outdoor daphnia cultures are more easily cared for. However their
productivity can be boosted by doing the same things.
This is more than you were asking for Ruruftyu. You probably are familiar
with most of this stuff. I hope there are things which you can gleen from
All the best!