Such chemicals may accumulate in reef aquaria and affect other animals. Although soft corals, leather corals, gorgonians and many other alcyonarians, are permanently attached to hard substrates, a few others primarily sea pens and their relatives are found in unconsolidated sediments and many of them are quite mobile. They may move up and down in the sediments many times each day or remain immobile for long periods of time and then become quite mobile for a short time. For more information about sea pens follow this link. There are many predators upon them.
Sea pens are soft-sediment dwelling soft corals that are often found in great beds.
In these situations, they act as a food resource for many different types of predators. A Caribbean gorgonian showing the snails, Cyphoma gibbosum , eating the flesh of the branches and a file fish which was plucking polyps off the branches. These snails can bore there way into a leather coral leaving only a small hole to mark their presence. Once inside they have the potential of completely eating the whole leather coral, but do it from the inside. The leather coral will appear to be fine, until one day it starts to disintegrate.