In article ,
Allan Adler wrote:

The plumber was just in my apartment to clear a clogged bathroom sink.
He pulled up the drain stopper and pointed out that it was all covered
with something he called "bacteria". It extended down to fill up the
trap. He snaked the pipe and let the debris fall into a bucket, which
he then dumped in the toilet, and pointed to a particularly large piece
that could have been the source of the problem. He says it is a common
problem in apartments.

I think it is the same as the kind of black or very dark green stuff I
sometimes see around the drain of the sink.

Anyway, I'd just like to know whether there is a kind of algae that does
this and whether in certain seasons it "blooms" and clogs up the pipes.

Algae are photosynthetic, and drains are kind of dark for photosynthesis.

Bathroom sink drains generally get clogged with hair, which gets wrapped
around structures in the drain. Other debris and soaps stick to the clots
and the whole mess is a good substrate for a large variety of microbes.
Soap is pretty nutritious stuff. This sort of mixed culture is sometimes
called biofilm and is very common on submerged or wet objects where there's
a source of nutrients.

The plumber recommends draining a couple of tablespoons of bleach in a
sinkful of water once a week. I don't know how environmentally friendly
that is. If the algae only blooms seasonally, I might be able to limit
the bleach treatment only to the season when the algae is in bloom.

Considering that a lot of people throw great slugs of bleach into their
washing machines, I wouldn't be too alarmed by a few tablespoons. Bleach
can break down hair, too, so it's not only the germicidal effect that
helps.

You could check the visible part at the top of your sink drain occasionally
to see if there's a hair present. Dangling from it out of sight is often
a big wad of crud. Break the hair and the crud will proceed down the
drain at an early stage before it threatens to block your sink.

As long as it is living in my apartment, I figure I might as well study it.
I have a microscope, even though I'm not very skilled at using it. It can
magnify from between about 50X to about 675X. I don't know if there is any
chance of identifying the exact species of algae (if that is what it is).

It's not algae but there's lots of other stuff in a wad of grunge from a
sink trap. I don't think you're going to identify the microbes, but you
can probably spot the hair without too much trouble. This assumes you
haven't flushed the toilet since the plumber dumped the crud in it, of
course! ;-)

All this probably belongs in a home maintenance newsgroup, or maybe a
basic life skills one.