Last week I emptied the tank, washed the sand, and replaced everything. As usual, I kept out the dirty water I'd washed the sand with, and let it sit overnight, just in case any tiny snails were hidden in the gunk. Normally, the dirt settles, and the snails climb to the top, where I catch them and return them to the tank, then dump the goopy mess.
But this time, there was a white network of fibers just on top of the settled gunk, below the inch or two of clear water. I stirred the water again, and let it sit. Two hours later, there was the net again. Three times I stirred it; every time, white lines made a road map along the top two hours later.
I looked at the clumps under the microscope: all I could see were tiny, straight threads. Watching one for a while, I could see it grow, lengthening at both ends. When I stirred the mix, I could still see shreds of threads, unconnected. But two hours later, there was the network again.
|Monday evening, overview. The bowl is 6 inches across. This is about a 3 inch section.|
I was gone for a day, and came back Wednesday afternoon. Part of the bowl was covered with a papery coat; the rest was still clumps of threads, some still making a road map.
|Zooming in, Wednesday afternoon.|
The filled-in areas looked like papier-mache pulp; all short, white fibers, arranged every which way.
|Thursday afternoon. The "roads" are gone, replaced by individual clumps.|
I looked at several of these clean clumps under the microscope. There was nothing to see but the white fibers, still short and straight, sticking out in all directions.
|Zooming in. Nothing but white fibers on the dark background.|
Over the weekend, the threads covered the whole area, without any organization into clumps or roads. When I shook the bowl Sunday night and again this morning, they disappeared, and returned in a couple of hours to the final, uniform covering. No roads, no clumps.
I don't even know where to start to find out what this was.