If you have a large aquarium, you are very fortunate. You can choose just about any fish on the market to fill your aquarium. No aquarium is too big for any type of fish. As you choose your fish, keep a few things in mind.
First, think about the size all your fish will be when they are full grown. You can have any fish you want, but make sure that they will be good tank mates when they are full grown. For example, neon tetras do not grow much longer than an inch, while rainbowfish can grow to over six inches, and will gladly feed on your neons. Do some research before buying any fish to make sure they will be compatible.
If you have a large tank, you may want to consider having a large school or two of small schooling fish. Consider buying schools that are in contrasting colors. This will create a pleasing effect, and the large space will allow your fish to swim in a pack.
If you are looking for larger fish, you may want to consider raising discus fish. These fish are not for beginning aquarium owners, as they can be delicate. They must have a tank of at least fifty gallons, and can grow up to eight inches. They are a peaceful fish and come in a variety of colors. Their name comes from their disc-like shape.
Angel fish are another type that do well in large tanks, as they need at least thirty gallons. They are easy to care for and grow to about six inches. The angelfish needs soft water, and can be shy, so it prefers a planted tank.
Bichir are large, eel-like fish that need at least fifty gallons of water. They can grow to close to two feet in length. Some varieties can actually spend a few minutes on land because of a specially designed swim bladder that allows them to breathe out of water. These are unique looking fish and need plenty of room to swim. They will swallow animals that can fit in their mouths, and they will attempt to jump from the tank.
Some species of freshwater sharks need large tanks. The Black Fin Shark should have around seventy gallons. These are easy to care for, and grow up to ten inches. They look mean, but they are not vicious. They will, however, swallow smaller fish that get in their paths. Black Fin Sharks are bottom feeders and enjoy living in small groups. Rainbow Sharks also do well in large tanks. They only grow to six inches, but need at least fifty gallons of swimming space. They tend to be territorial, and need room to establish their territory. They are aggressive towards other Rainbow Sharks.
Whatever fish you choose to keep in your large tank, make sure they are compatible with each other. Since you have the luxury of space, consider investing in some of the larger varieties. You will enjoy having fish that many of your fellow aquarium owners cannot have due to lack of space.