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Re: Daphnia and Green Water

>From: "James Purchase" <jpurch at interlog_com>
>Subject: RE: Daphnia and Green Water
>The recent posts about Daphnia's abilities to cure a tank with suspended
>green algae intrigued me. Over the weekend, I obtained a bag of Daphnia from
>a fellow member of my local plant group (thanks again Franc) and placed them
>in one of my plant grow out tanks, whcich doesn't have any fish but does
>have lots of suspended algae (due no doubt to me habit of keeping too many
>nutrients in the water column of this tank).
>Within 12 hours, the previously pea soup green water had cleared remarkably.
>(and the Daphnia were VERY green). I'm not interested in getting rid of all
>of the suspended algae in this tank, because then the Daphnia would starve,
>but I'd bet that they could do it if given the chance. In a tank with fish I
>guess the problem would be to maintain enough Daphnia to handle the
>suspended algae while avoiding the hungry mouths of the fish.
The Daphnia don't usually die out from starvation when they clear up the
green water.  They stop multiplying rapidly, and the population settles
down to a steady level.  In a tank with fish, the fish get them all---no
survivors!  I have tried "Daphnia cages", where the Daphnia are protected
from the fish by fine mesh netting.  These work, but you have to be very
careful in your choice of netting.  Common fabrics, such as nylon, dacron,
etc. give off toxic materials that can kill your plants.  I finally got a
netting made of some kind of teflon-like material that was inert and has no
effect on the plants.  Another thing about Daphnia is that they are
sensitive to high temperatures, and will all die out if the temp gets close
to 90 degrees F.  They don't do very well at 85 degrees, and really prefer
to be in the 70's.

Paul Krombholz, in soggy central Mississippi,  expecting some light frost