Re: red algae & CO2

> From: ac554 at freenet_carleton.ca (David Whittaker)
> Subject: PMDD Paper
> "Because others have observed that tanks with CO2 fertilization have
> relatively little red algae [5], it tempting to speculate that at
> least some red algaes are able to utilize bicarbonate, giving them an
> advantage in aquaria where most of the available carbon is in this
> form (typically those with high carbonate hardness and high pH)."
> "Red algae is favored over green algae if most of the available
> carbon is in the form of bicarbonates."
> While the red beard/brush algaes seem to take off when my DIY CO2
> runs out, that may simply be due to diminished competition with the
> plants. I wouldn't be tempted to conclude the above until I had
> better proof. It is a pretty broad generalization and there sure
> are a myriad of red algaes.

The relationship between brush algae and CO2 seems to be well founded
at least by anecdotal evidence. I can corroborate it personally.
The fact that other algaes don't seem to be affected as much as
brush algae to CO2 leads me to suspect that it's not a matter of
competition for nutrients that is inhibiting the brush algae. I
suspected pH or increased allelo-chemical production. 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 /

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 suspect I may have a slight deficiency of potassium since,
although it is contained in Flourish, it may be insufficient
and I am only dosing twice weekly. Lower leaves of the Giant Hygro
Stricta have yellowish holes and the E. amazonicus are not growing
as large as they should. I would say these problems are less in
evidence in the soil tank indicating that the soil is at least
partially compensating. I too am interested in comparisons of
nitrate & phosphate test kits. Is there a potassium test? The only
nitrate test I have seen so far is the Tetra one with a rather
limited supply of test (25 I recall) and the price was $20Cdn. }:-[
Likewise with the phosphate kit (20 dry tab tests) although 20
refills only costs $17 + 14% tax. -sigh-

I've observed the ratio of help-me type questions to technical
discussion has greatly reduced recently. Perhaps the nutrients
are being absorbed by the technical discussion and the help-me
questions are flourishing on the aquaria.freshwater.plants
newsgroup. ;-) Or perhaps the newbies prefer not to wade through
all the jargon. What's happening with the mailing-list subscription
size? Are some of us migrating to the newsgroup in quest of richer
grazing? Is our growth rate slowing?

Steve Pushak          spush at hcsd_hac.com     Vancouver, BC, Canada