Canon Elan IIe, tripod 380EX flash off-camera for partial sidelighting Sigma 105 EX Macro w/ 36mm extension tube Fuji Provia 100F f22 at 1/125

One of my favorites

In establishing and decorating my ecosystem, I gathered a few 'living rocks' from the river, stones with plant life and barnacles on them. One small stone the size of my palm turned out to be populated far better than I thought.

I had spotted the numerous barnacles, but what I didn't see in my flashlight beam was the colony of anemones all over the surface. Anemones contract themselves into a tight ball when danger threatens, so once I'd handled the rock they had made themselves practically indistinguishable from the stone itself. But after only a few minutes in my tank, they had 'blossomed' out into feeding mode, extending the stalk of their body and a bloom of small arms at the head.

A friend told me these were called 'Triffids', and would soon take over a tank. She was right. They reproduce like wildfire, dropping tiny ones from their bases, which then migrate around the area either by slow movement along the surface that they're anchored to, or be releasing themselves into a current to float along to a new location. And at any given time, I have dozens in my tank.

This is the largest example, and appears to be a different species from some of the others - others don't have the triangular mouth opening in the center, but rather a flat one. The full spread of arms around the head measures roughly 1.5 cm across. You're looking directly at the top of the anemone and straight into its mouth, which feeds directly into the stalk of the body. You can also see a sequence of this one feeding at this link.