Re: Control of green water with Daphnia

>Sep 21 10:47:00 1995
> From:       'veiga at lexmark_com'                               (BNR400)
> Subject:    Green Water Control with Daphnia
>Anyone out there tried to control algae bloom in your plant tanks
>using one or several of the Daphnia species? It would seem to be a
>very natural approach, as the Daphnia population would increased
>quickly with increased algae bloom, and correspondingly decrease with
>algae consumption.
>You couldn't have many fish (except algae eaters), but then fish
>aren't crucial to a planted tank.

I have controlled green water with Daphnia many times.  I normally grow my
plants without fish, but I have some tanks with fish.  I find that I have
to take all the fish out, even Corydoras catfish.  The Daphnia multiply
rapidly and clear up the green water.  I don't think it is a good idea to
return the fish immediately.  Wait a few weeks or months and let the plants
get well established, even to the point of being a bit crowded.
Reintroduce the fish gradually.  The tank should stay clear.  On some
occasions my daphnia have not multiplied and cleared up the green water,
and I have always found that adding nutrient solution makes the green water
become brighter green, and then the Daphnia start multiplying.  Apparently,
if deficient in nitrogen, and possibly other nutrients, the algae doesn't
have enough nutrition to allow the Daphnia to multiply.  I have seen this
requirement for additional nutrients perhaps a dozen times, and the Daphnia
have always responded to the addition of nutrients and done their job.  I
even worked out a kind of 'Daphnia cage' that can hold Daphnia in a tank
with fish and protect them from the fish.  The water circulates through the
cage and the Daphnia can keep it clear while you have fish in the tank.  I
did an article about the Daphnia cage in The Aquatic Gardener a few years

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174