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Red Algae

Steve Pushak wrote:

>If you have been unfortunate enough to get "black brush" algae, (furry
>short tufts) you can discourage the growth by keeping pH below 7. Its a
>marine algae and flourishes at high pH. 

Red algae are _not_ strictly marine.  While there the majority of the 4,000
or so species are marine, there are over 100 species of fresh water red
algae.  If you happen to have a species that is adapted to water with a
higher pH, dropping the pH may help get rid of it.  But there are other
species that will happily thrive at a pH of 6, or perhaps lower.  What they
all seem to have in common is that they thrive in situations of high
nitrate and phosphate.

Mark Fisher wrote:

>Seriously, though, the dreaded black brush algae is definitely a
>freshwater species.  The black/gray-green color is a characteristic of
>the freshwater red algae.  Marine red algae are red colored, due to the
>presence of the photosynthetic pigment phycoerthryin.  This pigment is
>greatly reduced in the freshwater species.

While this is generally true, I have some photos of some really attractive
RED red algae in a soft water, low pH discus tank belonging to a friend.
It was growing on some Bolbitis that was clearly deteriorating in the
soft/acid water.  I suspect that it was living on the nutrients that were
leaching from the dying leaves.   It was pretty enough that he actually
left in the tank for quite a while. (It did not spread beyond the sick

Karen Randall
Aquatic Gardeners Association