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Re: green water

Karen wrote:
> Steve wrote:
> 
> >One reason you probably can't test any nitrates or phosphates in the
> >green water is that they are in the biomass of the algae. The algae are
> >continuously being consumed and the nutrients recycled. What you want to
> >happen is for the nutrients to become locked up in the macrophytes, the
> >plants.
> 
> True
> 
> >This is also why, if there aren't sources of nutrients (ie decomposing
> >material), then flocullating and filtering the algae is a good way to
> >remove those nutrients from the system! Better than shutting off the
> >light because that kills the algae but doesn't remove the nutrients. The
> >plants, even in the dark, are still dutifully absorbing nutrients.
> 
> Yes, but you leave even one cell behind, and it quickly multiplies again.

The objective of filtering IMO, is not to remove all of the algae cells
but to remove the nutrients which the algae cells have captured in their
biomass. You could accomplish the same objective by simply replacing ALL
of the water in the tank. Since replacing all the water at once is not
very practical, you might have to perform 3 or 4 successive large water
changes. Unicellular algae are VERY effective at absorbing nutrients in
solution. They won't be able to capture all the nutrients if the
nutrients are coming from another source like the substrate, excess food
and fish or organic decay from something like a Crypt meltdown. They
only feed upon the nutrients in the water, so you still have to treat
the source of the problem too.

Another point to make is that a filter will not remove other mineral
nutrients which you might want to add to the water in order to ensure
that the macrophytes have an adequate supply in order to maintain their
growth rates to the point where they become the dominant consumers of
the phosphates that are feeding the algae bloom.

On the other side of the coin, you have to have a good filter in order
to capture green water algae. In my experience, sometimes that means
using 2 or 3 different filter cartridges or even replacing the entire
filter if its so old that the seals are no longer effective. Once the
seals are compromised or the filter cartridge gets leaky, it is no
longer effective at removing the unicellular algae. If you have a good
filter on hand, then I'd say that's the best method. If its not working
for you and cost is a concern, then the darkness method is going to be
the best alternative.

> One last thing about green water:  It's not dangerous, just annoying.  And
> it tends to go away eventually even if you do nothing.

It can persist for months. Its not dangerous for the fish, I agree, but
its competing for all of the nutrients in solution and its blocking the
light to the plants. I wouldn't leave it untreated. I think both
treatments, shading and water changes or filtering are effective.

-- 
Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!