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Re: Green water

Steve Pushak wrote...

>Paul Krombholz did a lot of experiments with green water and adding
>nutrients including nitrate and these are written up in TAG 4:2 and 5:2.
>According to Paul's data adding nitrate doesn't do anything but make the
>green water greener.

This is false. He says that he added Hoagland's Solution several
times to deal with the nitrate deficiency. Both the algae and the
plants got greener. Eventually the plants gained the upper hand.
I quote the first three sentences of the second article.

"About the fourth or fifth time I added Hoagland's Solution, an
interesting thing happened. The tank cleared up. It didn't happen
immediately, but over a period of about two weeks."

Maybe Paul would care to comment, since he wrote the two-part
article. It's actually an interesting little piece.

> I'm afraid I can't go along with the suggestion
>that green water is _caused_ by a shortage of nitrate. It results when
>conditions are favourable for the algae to grow.

Did someone suggest that green water is caused by a shortage of
nitrate? Roxanne left her tank unattended for a month. Who knows
what nutrients were or were not present. In any case the green
water got a foothold. Tanks with green water which I have tested
for nitrate have measured low to zero. Those on the list who
have green water might wish to perform the test.

Conditions favourable to the establishment of green water are
bright light and a pH>6.0. I cannot recall a case of green water
in a well-planted aquarium with large fish, only in those filled
with guppies of various sizes. Is this observation shared by
others on the list?

In his article Paul wrote that the disappearance of the algae
may have had more to do with plant mass and the number of filter-
feeding critters it was able to support. As plant mass increased,
so did the number of animals consuming planktonic algae.
Eventually they were able to clear the water.

This might explain why Roxanne's aquarium developed the green
water. As the hunger of the fish increased, they would have been
driven to searching out smaller prey including those creatures
which feed on the suspended algae. The system was thrown off
balance. The result was an algae bloom.

I have three tanks side by side with identical lighting. One is
pea soup. Maybe I'll perform a green transfusion to a healthy
tank in order to see if the problem corrects itself.

Dave Whittaker
ac554 at FreeNet_Carleton.ca