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Re: Blue-green Algae

>Date: Sun, 1 Mar 1998 18:32:29 -0500 (EST)
>From: ac554 at freenet_carleton.ca (David Whittaker)
>Subject: Re: Blue-green Algae
>Dean Sliger says...
>><< Why does  the water lettuce that I have in all 4 of my tanks grow blue 
>> green algae at the base of the root structure? It doesn't seem to be 
>> spreading beyond this small area. >>
>>Tim, I have had this same problem in the past both with water lettuce, water
>>hyacinth, and salvinia.  Not sure why it happens, but it's a dickens to
>>up!  Perhaps it's from these plants collecting nitrogen and other "stuff" in
>>their roots?
>If you'd like some unqualified speculation, my guess is that the area
>about the roots of these plants is less oxygenated than other spots
>in the tanks. This is because the submersed plants are pumping oxygen
>into the water column in their immediate vicinity while the floaters expel
>their oxygen into the air. They may also be creating an environment that
>facilitates nutrient availability about the roots.
>I've noticed the same phenomenon. How much circulation do you have in
>the tanks?
I think that Dave is on to something with his question about circulation.
My suspicion is that there is not a lot of circulation.... and the floating
plants have created a micro-enviroment around their roots .... locally
lowering the nutrient concentrations.  
Blue green algae are efficient at obtaining phosphorus and CO2 at low
concentrations (more efficient than green algae). Like other algae, they
can better establish in stagnant water. I suspect that moderate circulation
will help.