Amy Turco, age 13, of New Bedford, Mass., for her question: 

ARE THERE MANY KINDS OF KILLFISH?

Killfish is the common name for any of more than 300 species of very small, elongated fishes that can be found inhabiting fresh, brackish or salt waters in all warm regions of the world.

Killfish are usually about 12 inches in length or smaller and are brightly colored. Occasionally they are also striped with black. The fish are often used as bait and are sometimes kept in home aquariums, where they thrive on either prepared fish foods or shrimps, worms, or insect larva. They will also eat algae.

Killfish are oviparous, or egg laying. The striped topminnow is a common killfish off the eastern and southern coasts of the United States, and so is the mayfish.

The rainwater killfish is found in swamps and stagnant streams in the southeastern U.S. This fish and the plain top minnow of the central U.S. are useful because they eat mosquito larvae