Fill the bottom of a glass tank with small stones or pebbles. Place a handful of stones inside two or three shells, to weigh them down at the bottom of the tank.
Plant the elodea plants inside the tank, by anchoring the base of plants in between the stones. These submerged plants will produce nutrients and release them into the water.
Fill the tank with clean, purified water until it's 2 inches from the top.
Add a handful of duckweed to the aquarium. These green, seed-bearing leaves will float on the surface, promoting the growth of algae and plankton.
Drop two goldfish inside the tank, one male and one female. Add two snails and two shrimp.
Add a pinch of fish food to the tank, and close the lid. Repeat feedings every two to three days, as needed.