Beard Algae

Thanks to NeilFrank  for the nice review of the data on beard algae
(APL V2#80). I have a few questions and comments, which I hope will
start some interesting (and pleasant, please) discussion:

- You do not mention allelochemicals  as an additional way (other
than competition for nutrients) by which  higher plants can overcome
this type of algae. Is it due to lack of data on this subject, or to
the fact that you exclude the existence of this mechanism? The
reason I asked this question is that I had frequently and for long
periods of time excess Fe and macro- nutrients in my tanks, but no
beard algae (just tons of cyanobacteria!). I wonder if anything like
a direct inhibitory effect from plants played a role in avoiding
beard algae infestation. I would exclude competition from
cyanobacteria as well, since now they are gone, and no beard algae
are visible yet.

- Can you provide recommendations on the living conditions of your
japanese shrimps? I have located a local dealer that should receive
them shortly (last time he called them 'Guatemala Shrimps', but they
looked like C. japonica). I have soft water, and I wonder if this
could be a problem. Japan is also a temperate zone, and I wonder if
tropical temperatures throughout the year would be a concern.

- Clearly  the concept of 'sterilization' is not the main message
that comes from your review, but it prompts me to bring up the fact
that I do not agree with those who consider it as a factor to
prevent  algae infestations. I used bleach treatment of plants with
success, but mostly for cosmetic reasons, or in order to give
individual plants a chance to better recover from algae
My point is that I suspect that many algae are almost ubiquitous
(are we really sure that plants and fish are the main carriers? What
about air, dust particles and tapwater?), and apparently algae-free
tanks do carry small amounts of algae. They may however become
visibly infested if the conditions change in favor of algae, even
without any introduction of new plants or new fish. For example, I
have a 20 gal tank with good plant growth and a quite heavy fish
load. No visible algae problems. I have two small box filters on
this tank. Suddenly, a couple months ago, I noticed a bloom of
cyanobacteria everywhere, associated with a previously unseen growth
of beard algae on some plants only. No new fish or plants had been
introduced. However, after a while I realized that one of the two
filters was not functioning, with a  reduction of biological
filtration. Once the filter was fixed and the most severely affected
plants removed, the whole tank recovered promptly.  
Conversely, an algae infested plant introduced in a tank with
unfavorable environment for algae should recover without spreading
the problem.  I say "should" because I have much less experience
than other people on this list, and I have not really tested this
hypothesis. I am curious to see if other people have hypotheses or
facts that contradict my thoughts.

- I have soft water (~5 DH, ~3KH, pH ~6.5), and almost never see
beard algae despite high CO2 levels. I wonder if this is in
contraddiction with what you wrote in the section on CO2, or if
other factors explain it.

dionigi.maladorno at roche_com