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Re: Live Foods Digest V3 #192

Hello Jai,

First of all, you should keep all Daphnids in several containers, just
in case one of the cultures crashes -- which WILL happen if you are
trying for dense cultures. All of them need not be 25 gal., but you
definitely should have several backups.

The attainable density depends very much on the particular strain of
Daphnid that you have, on the food, temperature, etc. You have to
establish that for YOUR strain and conditions.

Too dense a culture either crashes -- all the animals die out, or it
becomes "static". In a static culture no more young are born, the
Daphnids mature and then slowly die out. A static culture can be saved
by subculturing AND waiting for a while until it again starts
reproducing. That can take a while, again depending on the particular
strain of animal.

So, watch for a healthy number of young in the culture. Once that starts
diminishing -- harvest and dilute at least 3-4 fold. 

The dilution is very important, because Daphnids seem to excrete some
physiological poisons ("Hemmungsstoffe") that inhibit reproduction/cause
crashes/stasis, etc.

Another warning sign is production of ephippia (resting eggs) that look
like a black speck on the back of the Daphnid. That also is a sign of
either overcrowding or starvation and leads to the death of the culture.

Hope this helps.



> Date: Mon, 23 Apr 2001 21:33:15 -0700 (PDT)
> From: Jai Mani
> Subject: Re: Daphnia Density
> Hi Guys,
>        I wanted to ask a question about Daphnia. I
> wanted to culture daphnia to a very high density, and
> would like to know what the highest quantity that can
> be harvested from a 25 gallon container everyday.
>        I just got a culture yesterday and this would
> be the first time that I am going to culture it. I was
> hoping that someone would have some sort of procedure
> or mention the methods to obtain high density
> cultures.. hope there is someone out there.
> I need to feed my fish. =(
> thanks,
> jai