Virgularia mirabilis is a sea pen of up to 60 cm tall.

OK, so having explained what a sea pen is, now let’s talk about how they live.

OK, so having explained what a sea pen is, now let's talk about how they live.

I will only mention one other animal, a zoophyte (I believe Virgularia Patagonica) a kind of sea-pen.

I will only mention one other animal, a zoophyte {allied to Virgularia*}/{(I believe Virgularia Patagonica)}, a kind of sea-pen.

I will only mention one other animal, a zoophyte (I believe Virgularia Patagonica), a kind of sea-pen.

In addition to the obvious requirements of excellent water conditions, making a sea pen happy generally involves two primary things:

In either case, a sea pen that does not stay put is a major danger to itself and to your aquarium.

Cavernularia obesa is actually an unusual sea pen because it has polyps sticking out of all sides, as you can see from this photo taken from above.

This photograph shows a cross-section of the internal skeleton of the deep-water sea pen Umbellula encrinus, a type of cold-water coral.

Furthermore, if the sediments are too coarse or the flow too low to be "rippled" by the currents in your tank, then the conditions are likely not appropriate to keep a sea pen.

Furthermore, if the sediments are too coarse or the flow too low to be “rippled” by the currents in your tank, then the conditions are likely not appropriate to keep a sea pen.

Although a sea pen is unlikely to sting another coral and seriously injure it, they do produce a variety of nasty chemicalsthat they use to defend themselves.

Although a sea pen is unlikely to sting another coral and seriously injure it, they do produce a variety of nasty chemicals that they use to defend themselves.

A sea pen with too shallow or too coarse of a sandbed will show a characteristic behavior of curling up on the bottom of the aquarium rather than burrowing in (Erhardt and Moosleitner 1997).