This first photo is as taken; despeckled, resized, and sharpened only. I left the "dust" in place; it's part of the action.
In the upper levels of the tank, like it would be on the intertidal flats, everything is in constant motion. Here, the red algae sways in the water, and a small family of blue anemones glued to a fragile blade waves its tentacles, hoping to catch some of the swimmers that muddy up the current. Behind, bubbles dance; large ones going down, from the pump; small ones heading back up to the surface, carrying goodies collected en route. Released at the top, the goodies float back down; more specks in the water.
This red algae gathers "dust". I pour clean water over it, or take it out and swish it around in fresh water, and it looks beautifully clean. A few minutes back in the tank, and it's covered in these little specks. Some may be sand, some is detritus, leftovers from critter meals or floating fragments of rotting eelgrass, and the rest is made up of small animals, copepods and amphipods eating detritus, and tiny worms eating copepods and amphipods.
And I hadn't even noticed the hermit until I looked at the photo. There's usually one or two hidden somewhere in this mess.
|Everything going at once|
On the other end of the tank, and up close to the wall, things are more peaceful.
|Leafy hornmouth snail, Ceratostoma foliatum, sleeping.|
The water is clearer away from the current; I removed only a handful of swimmers and a scratch on the glass. This snail eats barnacles; in between times, he wanders around the walls, then goes to sleep for a day or so.
His shell started out white and pink, but as he grows it gets craggier and darker. He's beginning to show the "leaves" that give him his name; for now, they're just sharp lengthwise ridges.
Setup for these photos: black poster board behind tank, white reflector above and on both sides, spotlight aimed at top reflector, flash ditto. This seems to work on the upper levels, but not down on the sand. More experimentation needed.