Fish are some the most interesting and varying types of animals in the animal kingdom. All fish are cold-blooded animals that live in the water. They have backbones, fins, and gills.

Types of Fish

Fish come in more varieties than any other group of vertebrate animals. There are 32,000 different species of fish. There are three major types or classes of fish including jawless, cartilaginous, and bony fish. An example of a jawless fish is the lamprey eel. Sharks are cartilaginous fish and the blue marlin is a bony fish.

Fish vary in all sorts of colours and sizes. Fish can be as large 40 ft long to 1/2 inch long. There are some animals that live in the water and we may think of as fish, but really aren’t classified by scientists as fish. These include whales, dolphins, octopus, and jellyfish.

They Breathe Water

All fish have gills that allow them to breathe water. Just like we use our lungs to exchange oxygen for carbon dioxide from the air, the gills of a fish perform a similar function from water. So fish still need oxygen to live, they just get it from the water instead of the air.

Where do they live?

Fish live in nearly every large body of water in the world including streams, rivers, ponds, lakes, and oceans. Some fish live on the surface of the water and some live in the very depths of the ocean. There are fish that live in fresh water and others that live in salt water.

What do they eat?

Some fish eat plant life. They may scrape algae off rocks or eat plants that grow in the ocean or sea. Some fish, called predators, prey on other fish and animals. The shark is a noted predator that hunts for prey. Other predators lay in wait for their prey by hiding in the sand or rocks in order to ambush their prey.

Groups of Fish

A group of fish is called a school. Some fish gather in schools so they are harder to catch. A predator will get confused when attacking a school and sometimes can’t catch any fish at all. A loose grouping of fish is called a shoal.

Biggest, Smallest, Fastest

The biggest, or heaviest, fish is the ocean sunfish which can weigh as much as 5,000 pounds (2,250 kg).

The longest fish is the whale shark which has been known to grow to over 40 feet long.

The fastest fish is a sailfish which can swim as fast as 110 kilometres per hour.

The smallest fish is the dwarf goby at only 9mm long.

Fish as Pets

A lot of people like to have fish as pets. There are special aquariums and food you can get to take care of your fish. They can be fun to have and also beautiful to look at. Although they are fairly easy to take care of as pets, you will need to do some work. You need to keep the aquarium clean and make sure to feed your fish the proper amount each day.

The goldfish is one of the most popular fish to keep as pets in aquariums, fish bowls, or small ponds. The scientific name, or species, for the goldfish is Carassius Auratus. They come from the family and order of the carp.

Size of your Aquarium

There are many types of aquariums out on the market such as rectangle, square, round or even hexi shaped. Making sure you have enough room in the area as to where is will be situated is always an important factor as well as knowing how many litres you are wanting your new tank to hold.

Species of Fish

When it comes to deciding what species of fish you will be housing. These factors are very important because it will allow you to know what size aquarium you will need to have, as certain species of fish all have their own personalities as well as the different sizes they will grow. Some fish like live plants where others prefer a rockier out crop. Asking questions before purchasing your fish as not all fish are able to live together.


The most important factor to remember before anything else regarding an aquarium and that is filtration. Filtration is most probably the first thing that a new hobbyist is never told correctly and that is the correct filtration for the size of their aquarium. There are a heap of excellent filtration products on the market such as Eheim, Fluval, Aqua One etc and knowing what size to use is very important. When purchasing a filter always make sure that is able to filter the total litres of the aquarium water 3 times in one hour. This calculation will makes sure that there is a sufficient amount of filtration running in the aquarium.


Most aquariums now days have their lighting units built in to them. Some older models will still have the florescent tubes running either Tropical or Sunlight whereas the newer model aquariums now are fitted with LED lighting. Making sure you have the correct lighting is very important especially if you are wanting to grow live aquatic plants. Many plants require a good amount of lighting in order to grow and stay healthy, but also knowing how many hours to run your lighting is just as important as not to grow algae in the aquarium.


Different species of fish like different types of foods. There are many varieties of foods now days on the market and feeding a good premium flake or pellet will bring out the best health for you fish. There of types such as Colour enhancing flakes, Bloodworms, Tubifex Worms, Algae Wafers and even gel forms that are great for a variety of species and are designed to keep your scaly friends in prime condition.

Maintenance and Chemistry

No matter what size your aquarium is, you will always need to perform some sort of maintenance and water change to keep you aquarium clean and free of pollutants. This is done so by using a vacuum gravel pump or cleaner. By using this device you will be removing any unwanted waste, old food and decaying matter out of the water which can cause deadly toxins to elevate to levels that can cause major sickness and even fatalities in the aquarium.

Using and adding a good water conditioner and beneficial bacteria to your aquarium after you gravel clean and water change will remove any chlorine, heavy metals and unwanted toxins in the aquarium. This is very important that you do this no matter what water is used to refill the aquarium again.


How big can a goldfish get?

Goldfish can vary in size depending on the type of goldfish as well as their environment. Some goldfish have been known to grow up to 2 feet long and nearly 10 pounds (5 kg). This is the rare goldfish, however. If you have yours in a fish bowl, don’t expect it to get much bigger than a few inches long.

What do goldfish look like?

There are many types or breeds of goldfish. They can vary in size, color, and shape. Many are orange-gold in color, but some are grayish-white with orange spots (like the comet goldfish) and some have black spots or are olive-green. There are fancy goldfish, like the Jikin, which has a butterfly or peacock type tail. The Egg-fish goldfish has a more rounded shape, sort of like an egg. One type of goldfish, the bubble eye goldfish, has big bubbly looking eyes that bulge out from its head. Pretty cool!

How long do goldfish live?

A well kept goldfish in the perfect environment can live for years. There are instances where goldfish have lived over 40 years. This type of longevity is rare, though, and many aquarium goldfish will live for 6 to 8 years when properly cared for.

Where do goldfish live?

Goldfish are a freshwater fish and like to live in water that is 10ºC to 25ºC. Many goldfish live in aquariums and small domesticated ponds, but some do live in the wild. In the wild they live in slow moving rivers, lakes, and ponds. They like to eat plants and insects when living in the wild. When living in aquariums, they like a lot of space. At least 40 litres of water for each fish, but the more space the better as this gives them more oxygen, which they get out of the water.

Where do goldfish come from?

Goldfish were originally from China. During the Tang Dynasty and the Song Dynasty the fish were bred for their golden colors. Later, goldfish became popular in Japan where many new breeds were introduced.

How smart are goldfish?

Goldfish might be a bit smarter than you think. Some goldfish can see and remember well enough to distinguish between people. They often notice the person that feeds them each day and will get excited when they see them. There have been cases where goldfish have been trained to do tricks like swim through mazes, swim through hoops, or even push a ball into a net.

Tropical Fish

Tropical fish are popular due to the wide variety of colours, patterns, shapes and sizes available, and these eclectic choices adds an exotic feel to any tank/aquarium.

However, you should note that they can require higher levels of care than cold water fish, and sometimes even specialist equipment like a heater, thermometer, air pump, etc. This is because tropical fish are used to warmer waters, so your tank water needs to remain consistent around 26 degrees Celsius, and the water needs to be fully oxygenated as well (hence the air pump).

In general, tropical fish can live peacefully, though keep in mind there are some breeds that are more territorial and/or aggressive, and are best kept on their own. Remember to check with the store specialist before purchasing, as you wouldn’t want to risk stressing any resident fish.

Types of tropical fish include: Guppie, Molly, Loach, Betta, Tetra, Barb.

Fun Facts about Fish


Fish are vertebrate animals that live in the water. Vertebrate means they have a spinal cord surrounded by bone or cartilage.


There are over 30000 known species of fish.


Fish have gills that extract oxygen from the water around them.


Many fish have an internal air bladder that helps them to float. Those that don’t, like sharks, must swim or they will sink.


Fish are covered in scales which are often covered in a layer of slime to help their movement through water.


Cleaner fish help out other fish by removing parasites and dead skin from their scales.


Tuna can swim at speeds of up to 70 kph.


All clownfish are born as males. When the dominant female of a group dies the largest male will turn itself into a female, this change cannot be reversed back.


Female clownfish lay around 1000 eggs, the male clownfish will guard the eggs.


Whales can’t swim backwards.

Useful Information

Happy and Healthy Fish

Keep your Fish Happy and Healthy


Goldfish Care Guide

What to expect from living with goldfish.


Tropical Fish Care Guide

What to expect from living with tropical fish.