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viruses and algea blooms

We have all had green water blooms. We all looked through the archives for
an answer. Then we tried various methods from darkening the tank to
filtration with ultra-fine filter materials. And, eventually, after some
time, the green water went away.
During the last year or so,  my friend and fellow -ADPer Franc Gorenc and I
have discussed the concept of viruses in aquariums. Especially, what effect
viruses might have on algae blooms such as green water.

In Natural Histroy 2/99 - Special Reports, February 1999, Volume 108,
appeared an article by Curtis A. Suttle titled "Do Viruses Control the
Oceans?" He writes: " Researchers ... of the Univesity of British Columbia
had managed to isolate a virus that infected phytoplankton..." and "
...sudden disappearance of phytoplankton blooms from various regions of the
ocean ... [are] consistent with the rapid spread of a viral infection."

Although I realize that the article is based on _marine_ environments which
are radically different from our freshwater tanks, I do wonder: Could it be
postulated that green water blooms are the result of an imbalance of algae
cells and algae-eating viruses in our aquariums?
Here are some additonal observations, questions. and thoughts:

1. algae blooms occur in bright light. The question is does the algae
benefit from the light or are the viruses being destroyed by the bright

2. An algae bloom cannot reliably be cured by water changes. Is it because a
water change does not change the relationship of algae cells to viruses in a
given water volume?

3. According to Suttle: "As soon as a particular planktonic host reaches a
high concentration, the virus specializing in that species will be able to
sweep rapidly  through the host population." Could we be seeing this in our
aquariums at times also - a quick, unexplained clearing of the green water

4. When we use the various methods of  darkening the tank, filtration,
coagulation etc., do we target the algae or do simply change the
relationship between hosts and viruses, so that the later become relatively
more numerous?

5. Why then, do some people battle green water for months at a time? In my
own experience, I had pea soup green water for 10 weeks. Apparently, some
viruses (lysogenic phages) remain dormant in their hosts until "an
environmental cue - such as exposure to sunlight or a sudden temperature
change - will trigger their own replication process..." and leave, and kill,
its host. Are we dealing with a number of different algae species and
different viruses in our tanks?

Unfortunately, I don't have the resources available to do decent experiments
on this. I am throwing this out into the APD in the hope to gather some
ideas and experiences.
For those of you who have green water, I have two suggestions:

1. try changing water with water from another "clean" tank, instead of tap
water, in the hope of raising the viral count (all the common "be careful of
desease" cautions apply!). Better yet, try and find water froma tank where
an algae bloom recently cleared.

2. try tiggering an "environmental cue" - change the tank's temperature
drastically (of course, after removing the fish) up or down.

In conclusion, I hope that I have added some new and useful ideas into the
green water debate and love to get some feedback.

Michael Eckardt