Young Naturalist Awards

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In urban areas where exotic wildlife seems all too distant, many people bring the natural world home in the form of an aquarium. I became a tropical fish enthusiast two years ago, when I explored the art and science of fishkeeping—the second most popular hobby in the United States. Thus, the world I explored was, in fact, one I had created—a 29-gallon tropical freshwater aquarium. After becoming an expert on water chemistry, aquarium mechanics, and the biology of various fish species, I assembled this glass-walled environment and watched its aquatic community flourish.

I had maintained this miniature ecosystem, home to seven fish species, for nearly a year—but how well did I truly know it? How was each species adapted to its own needs? What happened unseen at night and on the gravel bottom? How did fish that could never meet in nature interact? What behaviors occurred, unknown to me? I planned to answer these questions this winter and, in the process, learn more about the tiny world within my own.

The Environment
The aquarium is 12 inches wide, 29 inches long, and 18 inches high; its base is covered by an inch of brown gravel. Along the back wall are the power filter and heater, which maintain clear water at a constant 75°F. The pH rarely fluctuates from 7.0, an ideal level for a community aquarium. A piece of artificial driftwood and two black-and-white variegated rocks provide refuges, while ubiquitous clusters of elodea plants (Egeria densa) oxygenate the water. Each stalk in the towering aquatic forest is supple yet brittle, frilled with countless rings of three narrow, curling leaves. The electric-green leaf tissue is almost transparent, being only several cell layers thick. This plant can grow at a rate of an inch a day; I frequently trim these specimens to 15 inches.

Columbian ramshorn snails, Marisa rotula.

At least 50 Colombian ramshorn snails, Marisa rotula, glide over glass, plants, and rocks; they are the progeny of just four original snails of a prolific species. As unpopular as they are among many fishkeepers, the snails are efficient scavengers here. Snails of one variety are golden yellow and have no pattern on their amber shells, which resemble the horns of a ram. The shells are tightly coiled, with the rims a darker honey color. The snails of the second, more abundant type have deep brown, nearly black stripes that follow the spiral of the shell in parallel lines. Each pattern is unique; there are gold shells with brown markings, some brown with gold, and several split exactly down the middle. Sizes vary from 1.25 inches in diameter to 0.5 inches, for at least four "generations" are represented.

All move by means of a flowing elastic foot. This soft, translucent base, speckled with dull brown, is triangular, with thin, slowly undulating edges. A pair of threadlike antennae writhes fluidly, and a shorter pair, half the length of the first, is attached to the constantly munching mouth. This orifice is ovular and dilates to expose intricate, mechanical scraping structures—a series of increasingly smaller mouths inside each other.

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