Guest Author - Jilly Florio

It's not necessary to keep your aquarium light on all day, or even on much at all, for regular freshwater fish tanks. In fact, Unless you have live plants in your tank that will need to photosynthesize, it's even better if you don't automatically flick on that hood switch. Here´s why.

In the wild, freshwater fish live in lakes, rivers and streams, often hanging around shaded rocks, overhanging banks, and under aquatic vegetation. The sunlight these fish live in is filtered these things and by the water itself. Bright light, for most fishes, actually can be uncomfortable for them.

This being said, you may indeed purchase a light for your tank, but do not feel compelled to turn it on, unless you are 1. home and 2. in the mood to enjoy your tank. The ambient light from your lamps and windows actually does a better job simulating a comfortable light level all by itself.

Leaving the tank light on each day actually creates more work for you! In any tank, algae already present waits for an excess of light photons to reproduce. You know you are leaving the light on too much when you have a thick, healthy growth of algae on your glass, plastic plants and aquarium decorations.

When you have Live Aquatic Plants
For living plants you will indeed be forced to use those light bulbs quite a bit. Most Aquatic plants require 10 hours of bright illumination each day. With low-light aquatics, you may be able to get away with only four hours a day. Watch your plants and see if they are thriving - you may be able to cut back on lighting a bit. A range of 1-3 watts per gallon will provide excellent lighting for both your water plants' needs and for a nicely-lit fish display.

Natural Light
While we are on the suject, ensure your tank is never in direct sulight. Not only will you encourage a rampant algal bloom, but you will possibly cook your fish. If there is one thing all fish hate, it's a rapid change in water temperature - a sure route to having ill and weak fishes!


Lastly, most people prefer a florescent bulb for their tanks. These bulbs promote a better color to show off your fish, are more optimal for your aquatic plants (if you have them), are cheaper to run than incandescents, and will not raise the temperatures either. Incandescent bulbs get hot, and can burn you, or harm your fish.