One of the key decisions in getting a fish will be what tank to choose. You normally buy one tank and stick with it while you have the option of changing other components.
While it might seem to make sense to start small, a small tank can be REALLY hard to take care of. If you get something just a little bit off in a small tank, it makes a huge difference to the fish. If you get a few too many drops of a solution youre adding, its a huge amount for the tank. On the other hand, a big tank gives you lots of water to work with.
If something starts to go wrong, you have a lot of time to fix it. Also, they accumulate waste and get dirtier a lot slower than small tanks, so in the long run, you may actually be saving yourself time with a larger one.
In addition, consider what fish you are most interested in, and do research on the species--some look cute when they are young, but grow quite huge! Angelfish, plecos ("sucker fish"),
bala sharks, oscars and goldfish are just a few examples of fish that are often sold small but end up huge, the last 4 growing to over a foot as adults! They need their room to grow up healthy, so think of future needs when first buying the tank, or choose fish that stay small if you do not have the room or inclination to buy a larger tank.
So while you might want to save money in the beginning, go with the biggest tank you can afford. Itll give your fish lots of room to swim in, and itll mean that any mistakes you make dont result in instant death for your fish.
Be sure to get a sturdy stand for your tank. While the tank itself might not seem to be very heavy, dont forget that water weighs 8.2 pounds per gallon. This quickly adds up to an extremely heavy tank when its full of water AND full of things like gravel and rocks, which weigh even more! Be sure that the stand you have the tank on is able to support that weight. If it warps because of water damage, it can slowly produce shear stress on the tank, and you can risk leaks that can spell overnight disaster.
Tanks can be made of a few materials. The most common is glass with rubber aquarium sealent in the seams.
There are also tanks made of different types of acrylic. Acrylic scratches much easier than glass (a consideration if you need to regularly clean the surface of algae as many of us do), but modern acrylic has other advantages over glass, such as much greater strength, less weight, better heat insulation, greater visibility and light transmission for a "truer" image, lack of seams, and the ability to be molded into a variety of shapes and sizes. Here, I am mostly describing modern high quality acrylic, sometimes seen in more expensive marine tanks.
There are also smaller mini tanks made from cheaper acrylics and plastics. These may be made of thinner, poorer quality materials which are not as strong and can yellow over time. Most of the cheaper plastics are best avoided for display tank purposes. But in the end, the choice in tank material is one of personal preference.
You also where you will want to place it. Think of where it will be located, and measure this area out to make sure it fits in the space you planned it in. The best place to put a fishtank is in a nook or area where it can have high visibility and accessibility, but not be constantly disturbed by things like slamming doors and rowdy children. It should be in a relatively dark area, because the tank should have its own lights; being exposed to natural sunlight will usually only result in algae problems later. In considering tank shape, think not only of your own tastes for room decor, but also of the needs of your individual fish. Some, for example, are high speed swimmers (you can judge by their torpedo-like body shapes), and these fish prefer long, wide tanks. Danios, barbs, freshwater "sharks" (not speaking of true sharks) and rainbowfish are good examples of fish that like "long" tanks. Others, such as angelfish and discus, prefer "deep" tanks. In considering tank shape, also think about whether you will want a planted tank. Light has more difficulty penetrating to the bottom of a "deep" tank, and so you will need a stronger light if you decide to keep live plants.
Once you have settled on a tank that works well for you, its time for Choosing a Filter to make that tank into a home rather than just a container.