stylistic:style_transfer
Aquaria

The saltwater fishkeeping hobby has expanded, over recent years, to include reef tanks, fish tanks that include large amounts of live rock on which coral is allowed to grow and spread. These tanks are either kept in a natural-like state, with algae (sometimes in the form of an algae scrubber) and a deep sand bed providing filtration, or as "show tanks", with the rock kept largely bare of the algae and microfauna that would normally populate it, in order to appear neat and clean.

The most popular kind of coral kept is soft coral, especially zoanthids and mushroom corals, which are especially easy to grow and propagate in a wide variety of conditions, because they originate in enclosed parts of reefs where water conditions vary and lighting may be less reliable and direct. More serious fishkeepers may keep small polyp stony coral, which is from open, brightly lit reef conditions and therefore much more demanding, while large polyp stony coral is a sort of compromise between the two.