"Steve" wrote in message
...
I believe it is called coraline algae, although I am certain there
is a
more scientific name to it. For cleaning, I typically take a razor
blade to the glass for the stuff that will not come off. I have
not
seen any problems in doing this. Hope this helps, and I am sure
someone
with much more experience than me can provide an even better
answer!


Yep, Coraline. Razor works great, unless you have an acrylic tank.
One wrong move and your tank is marred for life. Try a credit card,
or hard plastic putty knife.

billy