Aquariums and Supplies

Choosing Your Aquarium
The general rule for the number of fish you can keep in a freshwater aquarium is one inch of fish to every square inch of surface area in your fish tank.  Others say it is one inch of fish for every gallon.  Either way, if you already know what types and quantities of fish you would like to keep in your aquarium, keep the number and their maximum size in mind when choosing your aquarium.

You will need to buy a hood for your aquarium so that fish can't jump out of your aquarium.  (Yes, they can jump out of the water!)  Most hoods contain a light, and if your doesn't, you will need to purchase a light.  You should plan on making sure that your aquarium is lit about 10 hours a day for fish and plants to thrive.

Location
There are several things to keep in mind when choosing the location of your aquarium.  Here are some tips:
Don't place an aquarium in front of a window or anywhere that gets direct sunlight.  This can cause unwanted fluctuations in temperature, evaporation, and excessive algae growth.
Keep it away from moving objects.  For example, a playroom for kids who play with balls or throw things around probably isn't a great location for obvious reasons.
You will need an outlet(s) close enough to your aquarium to be able to plug things in like the light, heater, and filter.
Make sure your aquarium is easily viewed.  After all, it's the whole point in setting up an aquarium, right?

Heaters
You will need a heater to maintain the temperature in your aquarium.  Most tropical freshwater fish need to be kept around 75 or 76 degrees Fahrenheit.  However, this is not true for all species like koi or goldfish, so research the temperatures required by the fish you intend to purchase.  Most heaters have adjustable thermostats.  Find one that includes suction cups for ease of placing in the aquarium.

Gravel
Most aquariums should include 1 1/2 to 3 inches of gravel.  Some fish prefer sand.  Research what types of gravel the fish you intend to purchase prefer.