Re: fw red algae & CO2

>From: Kevin Conlin <kcconlin at cae_ca>
>Date: Thu, 04 Apr 1996 17:42:05 -0500

>Blatant speculation on my part (and clearly labeled as such).
>Baensch and others note that red algae seems to disappear with
>CO2 fertilization.  I was hoping that someone would come forward
>with data from real studies.  Somewhere there is someone studying
>freshwater red algaes for his PhD; would this person please step
>forward?  We won't make fun of you, really we won't.
I can tell you about references from the 70's and 80's, so I suspect that
there is even better stuff available today...

Back in the late 1980's when I first investigated red algae in fw aquaria, I
published a 4 part article on fw algae: FAMA (October 1986-January 1987). I
discussed red algae, CO2 and a variety of other topics.

Re: CO2, I derived information from 2 references:
Goldman. Carbon Dioxide and pH: Effect on Species succession in ALgae.
Science, October 19, 1973

Lemon (ed.) Carbon Dioxide and Plants. AAAS Selected Symposium (1984)

Here is a passage from my paper: 
"Red algae primarily utilize free CO2 and are naturally found in soft waters
of relatively low pH or streams where CO2 concentrations are relatively
high. Their native stream habitat explains why these furry epiphytes are so
tenacious and will not disattach conveniently from plants. In my experience,
the red algae are only found to be fully developed and to be grwoing
profusely in acidic conditions. In fact, when a local Raleigh aquarium shop
owner buffered the water to neutal in the store's front display tank, the
algae died back considerably. The change was not permanent, but supports the
notion that acidic conditions are needed for optimal growth. These
observations seem to contradict the advice of the Germans. They recommend
introduction of CO2 to suppress the growth of red algae

[As I indicated elsewhere, I never saw mature red algae in my tanganyikan
tanks where I suspect free CO2 shifted to bicarbonates]

The FAMA article also says.......
"It has been shown that the addition of gaseous CO2 or lowering of PH
stimulated the shift from blue-greens to green algae. This shift can occur
when stratified water conditions are artificailally circulated or
aerated.... causing CO2 to enter from the atmosphere."


From: Stephen.Pushak at saudan_HAC.COM
Date: Thu, 4 Apr 96 18:01:58 PST
Subject: Re: red algae & CO2

> It would be
>enlightening to see how a tank of brush algae and CO2 injection
>would fare without plants. This would demonstrate whether it was
>a pH or CO2 reaction or a matter of competition for nutrients /

I have seen many fw tanks without vascular plants with lots of red algae.
Often, these are growing on drift wood, but not always. In my experience
these tanks always had lower pH, lower KH where the dissolved carbon shifts
to CO2 as opposed to bicarbonates.

>Thread algae in particular seems to thrive in a CO2 rich environment
>where we might expect to see it inhibited in the same manner as brush
>algae by a lack of nutrients. Or maybe it's just more adept at
>utilizing available nutrients in short supply? If I were to reduce
>my phosphate concentration, through water changes or improving
>the nitrogen, potassium supplies, it would be interesting to
>see if this algae dies off or at least propagates less vigorously.

I tend to think that the algae progression from bg to greens continues to
the green thread algae and red algae. Are these the 'higher forms' of algae
that are more similar to 'real' plants.<g> Anyway, with enough vascular
plants, high light, CO2 and nutrient conditions that favor great plant
growth, many algaes can be virtually invisible while red algae or thread
algae may fluourish. I do not have red algae anymore in my tanks, but
occassionally get thread algae (especially the coarse branching one which is
either Pithophora or Chadophora). In many of my tanks, I never have to clean
the inside glass and do not have anything visible, growing on the plants
(except for small patches of thread algae around some fine leaf plants or
roots which can be physically removed). Not a big problem for me, but it
would be better to pre-treat the plants with bleach <g>.

The P reducing methods advocated by Conlin/Sears have worked for me to help
reduce thread algae and I am now going to re-confirm with a nice batch algae
that I have allowed to develop. BTW, these methods could probably affect
java fern and other epiphytes which do not directly derive their nutrients
from the substrate.

Neil Frank, TAG editor    Aquatic Gardeners Association    Raleigh, NC USA