This is a marine worm, Dinophilus, and it’s parasitized by unicellular organisms called Grellia. You can see the parasites as blue, banana-shaped structures in this polarized view. . Dinophilus are a few millimeters in length and inhabit all marine environments. They eat algae and mind their own business without bothering anyone. However, the large population I had in one of my fishless tanks were all infected by a species of unicellular organism. . When I checked an odd-looking Dinophilus under

Live sole or false sole What’s the difference, and why does it matter? The sole is the weight-sharing surface between wall and frog, made from keratin, very similar to the wall. A healthy sole builds a thick protective callus. We protect that callus rather than thin it. Live sole Firm with a slight waxy sheen. Blends smoothly into frog and bars. False or retained sole Dead material that has not shed yet. Looks chalky or crumbly in wet climates. In dry it may flake in sheets or lift at the edges,