Clownfish

• Because of the success of a certain children's cartoon, clownfish are a popular choice for aquariums. The needs of clownfish mean that you have to have a 20-gallon saltwater aquarium. Because clownfish are aggressive, you shouldn't have more than one per tank. In the wild, clownfish cohabitate with sea anemones for protection from predators; however, in a tank there are no predators. Therefore you don't need to include an anemone with your fish.
  
  

Goldfish

• Although goldfish are the most common type of fish for aquariums, not all goldfish are kept under ideal conditions. In order to maintain cleanliness in a tank, it's best to house one small goldfish per ten gallons in an aquarium. This is because goldfish are messy fish. Most goldfish are heavy eaters, and produce a lot of waste. A goldfish tank should be equipped to filter ammonia from the water. Goldfish are cold water fish, and do well in an aquarium with lower temperatures. It's possible to overfeed a goldfish, so if possible, ration out your fish's food.
  
  

Betta

• Many people have seen the betta, also known as the Siamese fighting fish, in big box discount stores, usually being sold in a one-cup container or along with a lily or stalk of bamboo in a glass vase. Betas are surface breathing fish that live in marshy areas. Because of this, they can dwell in a small habitat and require no filtration. Because bettas are tropical fish, they should be kept in water that is at least 72 degrees. A betta tank should have some type of lid or mesh screen to prevent them from jumping out.
  
  

Neon Tetras

• Neon tetras are small, even tempered freshwater fish with brightly colored scales. The fish rarely grow very big and typically do well in groups or 'shoals' of ten or more. A tank should have slightly acidic, soft water and plants. Larger fish such as angle fish may look at tetras as food, so it is not a good idea to have both types of fish in the same aquarium.
  
  

Plecos

• Pterygoplichthys, or plecos for short, are a hearty South American fish that live on plant matter. Plecos are frequently included in an aquarium to help stem the algae growth on the sides of the tank. Plecos are a catfish species that can grow up to two feet in size. However, most plecos will not reach that size in a smaller aquarium. Although Plecos are a tropical fish, they can endure colder water temperatures. If you keep a pleco under ideal water conditions, it may live for up to 10 years.