ref:This may be the wrong place to ask this question but . . .

["Matthew Simmons" <matt_simmons at ntlworld.com>]

Hi Fran,

You don't say anything about lighting in the tank but I am assuming that you
have the regulation one or two tubes for a fish tank.  The dark algae you
are accumulating is probably either brown diatomaceous or green spot that
has built up and in layers tends to look dark brown or black.  If its brown
algae its soft and comes off easily by gently rubbing the plants but to be
honest, IME if its brown your plec should be getting rid.  I suspect its
layers of the green spot you have on the glass.  You will have to scrub each
leaf with an abrasive pan scraper or algae pad - good luck!  You could try
soaking the plants in a bucket of mild bleach solution (not in the tank
:-))but thoroughly rinse and soak the plants afterwards in lots of fresh
water - this was an old remedy for black algae - you will find references
and advice on the Krib.

Why don't you get some more bogwood and use lots of java fern.  Simply tie
it to the bog wood and it will quickly root over it - the leaves will go
black over time but you can chop them out allowing fresh ones to show
through.  Its a very robust plant and impossible to kill - survives low
light, works better with a little CO2 but just don't plant it in the
gravel - it hates it.

Good luck

Matthew