Facts for Kids

Aquarium means a container that holds water and has at least one clear side so you can see inside. People keep fish, tiny crabs, snails, frogs, turtles, and water plants in aquariums. Some are small enough for one desk and some are huge like those at public aquariums where you can see sharks and penguins.

The word aquarium was made by the English naturalist Philip Henry Gosse from the Latin word aqua (water) and a ending that means “place.” Scientists like Robert Warington showed that plants in water make oxygen, which helps fish live, so a balanced aquarium can keep animals and plants together. Would you like to look into one up close?

Nano aquariums are very small tanks, usually under 75 liters (about 20 gallons). They can be freshwater or saltwater and show tiny, complete little worlds with small fish, plants, or shrimp. Their small size means you choose decorations and plants carefully so the animals have places to hide.

Most aquariums also have a few important parts: a filtration system to keep the water clean, lights so plants can grow and fish look bright, a heater for tropical tanks, and pumps or air stones to move water and add oxygen. A hood helps stop splashes and a strong, level stand holds the tank safely. Simple tools like thermometers and timers make taking care easier.

People began keeping water animals for study and display in the early 1800s. Jeanne Villepreux-Power made early aquaria in 1832 to learn about sea creatures. Nathaniel Bagshaw Ward used ideas from his plant cases to keep tropical animals. Anne Thynne kept corals and seaweed alive for years and helped show how marine aquaria could work.

In 1850 Robert Warington wrote about how water plants make oxygen for animals. Fancy iron and glass tanks at the 1851 Great Exhibition made people excited. Philip Henry Gosse opened a public aquarium in London in 1853 and wrote the first guide, so the hobby spread to other countries by the late 1800s.

The first part to know is the nitrogen cycle. In an aquarium, fish and other animals make waste that turns into ammonia, which is harmful if it builds up. Tiny helpful bacteria called Nitrosomonas change ammonia into nitrite, and other bacteria like Nitrospira change nitrite into nitrate, which is less dangerous.

Aquatic plants also help by using ammonia and nitrate to grow. If nitrate builds up, you must remove some water or take away nitrate by growing and harvesting plants. Some hobbyists use special low‑oxygen filters (called anoxic filtration) where other bacteria can remove nitrogen in different ways. Want to try spotting where these bacteria live in a real tank?

Freshwater, brackish, and saltwater describe how much salt is in aquarium water. Freshwater has very little salt, brackish water is a mix like where rivers meet the sea, and saltwater is like the ocean. Water also has a pH (how acidic or alkaline it is) and measures called hardness that tell how many minerals are dissolved in it.

To keep animals healthy you test the water, treat tap water so chemicals are safe, and add special salt mixes for marine tanks. Keep temperature steady (tropical tanks are around 25°C), do regular small water changes, and clean filters when needed. Careful checks help plants and animals stay happy—what would you test first in your tank?

A public aquarium is a place you can visit to see many tanks and very large exhibits. Some have small displays for fish and plants and giant tanks for big animals like sharks or whales. Others focus on dolphins, penguins, or otters that live partly on land and water.

These facilities build habitats that try to match an animal’s home, and they have staff who care for animals and teach visitors. Public aquaria are found around the world and sometimes join parks that focus on marine life. Which big sea animal would you like to see in a big tank?

Aquariums come in many sizes, from a small bowl for one tiny fish to a huge tank that looks like the ocean. You can sort aquaria by water type: freshwater (easy and common), marine (saltwater, more work), and brackish (a mix of both).

You can also group tanks by temperature — tropical for warm‑water fish or coldwater for species from cooler places. Other kinds are reef aquaria for corals, community tanks with peaceful species, aggressive tanks for feistier fish, specimen tanks for one species, and biotope aquaria that copy a real place with matching plants and decorations.