Tropical fish tanks are not all that different from other types of fish tanks. There are a few differences in the requirements, though, that do need to be taken in to account. When considering purchasing a tropical fish tank, you must first decide whether you prefer a freshwater or saltwater tropical tank, as the two require slightly different supplies and care.
For any type of fish tank, tropical or otherwise, have some kind of gravel lining the bottom two inches or so of the tank; you can also use sand. Gravel will help to conceal some of the fish waste to cut down on tank cleaning and also allows for the growth of some good bacteria that is necessary in the tank--not to mention it looks nice.
The filter is probably one of the most important parts of a tropical fish tank for both freshwater and saltwater versions. It serves several purposes--filtering out particles floating in the water, allowing the growth of bacteria in the filter that convert nitrite into nitrate, and also filtering out fish waste to reduce odours in the tank.
The heater is used to maintain the temperature of the water regardless of temperature changes outside of the tank. Tropical fish are used to warmer waters, so it is important to keep the temperature regulated at all times.
A tank hood is necessary for a tropical fish tank in order to keep the fish in the tank. Fish will occasionally jump, and without the hood, they may fly out of the tank. The hood will also help the heater in regulating the water temperature.