Ank. Tanks are available in various sizes, but if you plan to own multiple fish or very large fish, you need more than a simple fish bowl. A general rule is that each fish requires one gallon of water. If you plan to purchase fifteen fish, an appropriate tank will hold an absolute minimum of fifteen gallons of water.

Aquarium stand. A single gallon of water weighs approximately eight pounds, so you can understand why an aquarium that holds several gallons of water requires a strong, sturdy, supportive base. When choosing a stand, consider the amount of available space in your home. You may also want to think about buying a stand with storage space for cleaning supplies, fish food, books, and other materials.

Light. Fluorescent lights are an excellent choice for aquariums because they emit very little heat. In addition, fluorescent light appears filtered, so it more closely resembles rays of sunlight reaching into the ocean.

Heater and thermometer. A heater maintains the temperature of an aquarium, which is usually between 73 and 82 degrees Fahrenheit. Heaters vary depending on the size and volume of the tank. A thermometer gauges the water temperature so you can ensure that it remains in the appropriate range. Research the fish you plan to buy, because different types of fish require different water temperatures.

Filter. A filter eliminates harmful waste and other impurities from the water. A filter ensures that the water in your aquarium stays clean so that your fish remain healthy.

Gravel, rocks, and plants. Such decorations not only add visual interest to your aquarium, but give your timid fish places to hide and your adventurous fish places to explore. Aquarium gravel, rocks, and plants may be natural or artificial, and they vary in quality and price.

Water-testing kits. Water-testing kits measure pH (acid and base levels) and salinity (salt levels) in aquariums. In the wild, fish live in a variety of environments, but in an aquarium, even minor differences in pH and salinity can affect their chances of survival.

Fish food. Some fish require a quick sprinkle of dried flakes, while others have a more delicate diet that includes a blend of frozen brine shrimp, fish eggs, or algae.

Aquarium Assembly
3After acquiring all of your aquarium equipment, the following steps will help you assemble it. First, set up the aquarium stand and tank. Thoroughly rinse everything with water before you put it into the tank. Do NOT use soap because soap residue can affect pH levels in the water and harm fish. Next, attach the water filter, and place gravel, rocks, and plants in the tank. When everything else is in position, add water and attach the heater. Then, wait a few days and test the water. When the temperature, salinity, and pH reach their appropriate ranges, you can finally add the fish! Continue to monitor the temperature, salinity, and pH of the water, and clean the tank regularly.

Read the passage on the left to answer the following questions:
20)
How can the organization of this passage best be described?
A) chronological order
B) order of importance
C) classification/division
D) comparison and contrast
21)
The bulleted subheadings allow the reader to understand what about the text?
A) How aquariums are different from the wild and what kinds of fish and creatures can survive in an aquarium.
B) That there are multiple important parts of a successful aquarium and that each part takes a bit of explanation.
C) Why aquariums are important to the world of science to the understanding that scientists seek in the natural world.
D) How much each part of an aquarium costs with detailed cost breakdowns, material lists, and suggestions for where to buy.