The Ultimate Bug Gun!

An Archerfish's (or 'Spinnerfish' as they are sometimes referred to) body is deep and laterally compressed in shape, and has a mouth that is protractile (capable of being thrust out from its snout), where the lower jaw juts out. The adult sizes in this genus are generally small (5–10 cm) although the largest, Toxites chatareus, can reach a length of up to 40 cm. Probably the best known species kept in aquariums is Toxites jaculatrix, which is a silver fish with black stripes and grows to around 20 cm in length.

Archerfish are remarkably accurate with their water jets and adult fish invariably always hit the target with their first shot! They can bring down most insects and other prey (e.g. grasshoppers, spiders and butterflies) that are discovered resting on overhanging foliage. So precise is their aim they can successfully do this up to a staggering 3m above the water's surface! This is partially due to their phenomenal eyesight, as well as their amazing ability to compensate for the refraction of light as it passes through the air-water interface. There is no luck involved with their shooting ability, but rather has been proven to be an exact science. In fact Archerfish typically spit at their prey at a mean angle of approximately 74 degrees from the horizontal, but can still accurately aim when spitting at angles from between 45 to 110 degrees.

In order to achieve this accuracy when an Archerfish selects its prey, it has to rotate its eye so that the image of the prey falls on a particular portion of the eye (in the ventral temporal periphery of the retina) and ensure its lips just break the water's surface. It then squirts a jet of water at its victim using the narrow groove in the roof of its mouth. By pressing its tongue against this groove to form a narrow channel, an Archerfish then contracts its gill covers to force a powerful jet of water through the channel. The resulting 'bullet' of water can be up to 2–5 cm long, and accurately allows them to shoot insects up to 3m away, depending on the size of the prey. Archerfish are also able to alter the power behind the shot in accordance to the size of the prey item. And if the first shot does not knock the victim into the water, the archerfish will keep trying until it becomes dislodged. Alternatively, Archerfish will often leap out of the water to directly grab an insect in their mouth, if it happens to be within reach. 

But no Archerfish starts life with the ability to achieve this awesome accuracy. This takes much experience and time, and 'target practice school' starts when they reach about 2.5 cm in length. Due to this initial inaccuracy and until they've developed their skills, young Archerfish tend to hunt in small schools. This way, the probability is greatly enhanced so at least one jet will hit its target and the juveniles will get some food!