Soapfish are a marine species belonging to the family Serranidae and order Perciformes. Groupers serve as their closest relatives. There are at least 9 genera and 24 different species separated between two tribes, the Diplioprionini and Grammistinae. At least 3 of these genera belong to the Diplioprionini tribe and 8 genera to the Grammistinae tribe. Soapfish are widespread across the Eastern and Western Atlantic to the Indo-Pacific region, including the Red Sea. They can be found at depths between 1-65 m.
All soapfish are rather small, with the largest only growing to be 30 cm in length. Coloration and patterns vary greatly based on the species. For example, the greater soapfish is more brown in color with white speckles while the sixstriped soapfish has a brown body marked by up to six yellow or white horizontal stripes. All soapfish have a reduced spinous dorsal fin and a slightly protruding lower jaw. Members of the Diplioprionini tribe have one or two dorsal fins that are deeply notched and ctenoid scales. Their bodies are also a lot deeper than other soapfish and have very long pelvic fins that extend back beyond the front of the anal fin.
Soapfish are named after their ability to produce a toxic body mucus that forms a slimy, soap like froth when secreted into the water. This occurs when under stress and acts as a defense mechanism against predators. Their diet consists of small crustaceans and fish, and the majority of soapfish are nocturnal hunters. Two soapfish from the Diplioprion genus are active during the day though. Soapfish may implement a variety of hunting techniques depending upon the species. They can be spotted with a head down posture inspecting the sea floor for prey. Some, like the yellowface soapfish, will swim alongside larger fish to use them as cover to sneak up on their prey. They’ll also pounce on smaller prey flushed out by other species such as catfish.
Soapfish are durable enough for aquariums, but their aquarists should keep them separate from other fish to avoid their secretion ability harming them. Back in 2008, the only soapfish noted as vulnerable by the International Union for Conservation of Nature (IUCN) was the socorran soapfish. Climate change and severe weather will shift and alter their habitats and cause extreme temperature changes. Otherwise, the majority of other soapfish species are listed as least concern by the IUCN.