I've seen this before in my tank, but never realized that it only took 1 or 2 days for it to 'show up'.
It is located directly below the hairy mushrooms that my clowns call home. I'm not sure if it 'showed up' today or yesterday. I've been working late this week and haven't been paying attention that close.
"When they was no meat we ate fowl, when there was no fowl we ate crawdad. And when there was no crawdad to be found, we ate sand."--Cellmate
"You ate what?"--H.I.
"We ate sand."--Cellmate
"You ate sand?"--H.I.
"That's right."--Cellmate