LEDs (light emitting diodes) consume very little electricity, they run on DC (direct current) and IMO most energy efficient mode of creating lighting. They are also cheap and if organized properly, can light up dark areas.

Another use can be using different color leds and using them to light up different areas in your Aquarium.

I have started tinkering with these leds, you will see two led boards on this aquarium, each PCB (printed circuit board has 220 leds and powered by a small mobile charger.

each board has cost me around Pakistan Rs. 1,000/=, US $ 13 to assemble.

The cost of assemble is high, but they will repay their cost of ownership from the savings in my monthly electric bill.

Your comments and suggestions for improvement are welcome