Chris Hogg wrote:
The sludge in my tank is much too soft to offer resistance to a board
as you describe, especially as it will be trying to float if it's
wood. In the past I've gently lowered a long bamboo into the tank
until it touches bottom. Then _slowly_ withdraw it. The bottom end of
the bamboo comes out black along its length where the sludge sticks,
to the depth of the sludge. If you pull out the bamboo too quickly,
the sludge can wash off. Wash hands after use!

Thanks, Chris. And the rougher the bamboo the better, so the sludge
sticks to it? No need for the board business, then. (I often go into
overkill.)

Eddy.