Instructions
Determine what types of fish and plants you want to keep in your tank. Some fish do better in lower light, but live plants require special types of lighting in order to thrive.
Know that there are four different categories of aquarium lights. Lowest to highest in intensity and cost, these are: standard fluorescent, compact fluorescent, very high output (VHO) and metal halide.
Use standard fluorescent lights if you want in smaller tanks (under 20 gallons) or tanks where you don't plan to keep live plants. These are adequate and are the least expensive, so they're a good place to start if you're new to the hobby.
Compact fluorescent lights are a good choice for regular planted tanks of moderate height. Depending on the tank size, you can use this type of lighting for 55-gallon tanks and possibly even 75- or 100-gallon if your plants don't require high lighting.
Install VHO lights when you need high light. This type of lighting can penetrate deeper into your tank and provide better light for your plants.
Metal halide lights provide point-source lighting, which is the closest thing to sunlight. These lights are rarely used in freshwater tanks because they're not usually necessary.
How to Choose Lights for a Freshwater Aquarium
Choosing lights for your aquarium may seem like a simple task, but in truth it's an involved process that requires a great deal of consideration. Your lighting needs are determined by several factors. The choice of lights for a freshwater aquarium can make a huge difference in the productivity and visual appeal of your fish tank.