post image

Choosing a Unicornfish

A close relative of the tangs and surgeonfish, the unicornfish is also a common inhabitant of Indo Pacific, Red Sea and East African reefs. They are even found off the waters of Hawaii and Japan.

These herbivores look much like tangs. They have dorsal and anal spines and a horn-like appendage sticking from between their eye (the rostrom) from which they get their name. The males tend to have a better developed horn.

In nature, they are often found swimming in groups. They are mainly day-time fish, feeding on leafy brown algae like Sargassum. These fish are found in coral reefs, patch reef and tropical rocky areas. In an aquarium setting, be sure to have an ample source of leafy algae on which these fish can graze.

These fish require fairly good water quality with low ammonia, nitrate and nitrite levels. They do well in temperatures of anywhere from 76 to 83 degrees Fahrenhiet, a “normal” pH of 8.3 and a normal salinity.


Unicornfish are good to keep with other fish, and don’t show aggression towards their own species. The largest specimen was found off of Florida at 2 feet and 4 inches. In your tank, they won’t get that big, usually staying at a length of about 7 inches or so.

This fish has been found carrying ciguatera, a micro-organism that is toxic if consumed. However, it does the fish, its host, no harm. Many herbivores around reefs contract ciguatera, then are themselves eaten by carnivorous fish. The toxin is passed to the carnivore, which could be caught for human consumption. The toxin is dangerous to humans and could cause serious medical problems if eaten. Barracuda are other fish known to carry the toxin, particularly the adults who have had time to accumulate the toxin in their systems. But unless you plan on eating your pet, there is no danger of ciguatera poisoning to you.

The bluespine unicornfish (Naso unicornis) is a common species found in the Indo-Pacifc region and the Red Sea. It is fairly hardy, but can’t be kept with aggressive species. Otherwise, finding a unicornfish when you’re ready to own one is often just dumb luck. In some cases, you can special order these creatures as well.