Black algae; Carbonate hardness

Hey all!

Another lurker coming clean and yet more newbie questions.  First, some
I have a 55 gal tank, temp 80 F, ph=6.4/6.6, no ammonia, no nitrites, slight
measure of nitrates, no phosphates.  With a tetra kit, the GH took 3 drops
and the KH took 1 drop to make the described color changes.  I admit
confusion about the measurement:  degrees? ppm?

My fish are a 4" angel, 3 harlequin rasboras, 6 growing false siamensis
(<sigh> a bum steer from the fish store), 5 long-fin danios, 2 brown
spiketail paradise fish, 1 brilliant rasbora, 1 black tetra, 1 sunset
gourami, and 3 corys.  I use a Penguin 300 filter without the biowheels.

My plants are 5 generic swords, 1 mellon sword, hydrophila, java moss and
fern, 5 small banana plants, and ludwigia growing in a gravel substrate under
70 watts of light (not enough, I know, but working none the less) and
everything taking off since the advent of yeast CO2 a couple of weeks ago.

?#1.  The swords are now growing faster than I am picking off the
black-algae-infected leaves so now the bulk of my algae is growing on a med
large piece of driftwood.  If I remove it and give it the copper or bleach
treatment will it absorb the chemical and introduce it into the tank?  Or
should I remove the java fern, sacrifice the java moss and boil the whole
thing?  I like the way it looks in my tank and I'd rather not remove it
permenately.  The rest of the algae is growing on mechanical equipement which
I can bleach.

?#2.  I realize from what I have been reading on this list that my KH is very
low.  The whole system looks good, fish are healthy, and I have been testing
the ph frequently since introducing the CO2 and there haven't been any large
fluctuations.  But I realize now that lack of buffering was probably at the
root of some severe problems I experienced about 6 months ago.  I add baking
soda to raise the KH?  How much?  How often? With water changes  (which I do
weekly to bi weekly) ?

Thanks very much for your help and suggestions.  I've gotten more concrete
and usable advise from 1 month on this list than I've gathered in the last 5
years of aquarium keeping.  Yes, I admit it!! An aquarium for 5 years and
still a newbie!!!!

Mary Gale Woolford
Mobile, Alabama