Natural lighting?

[iswimwithmyfish]

is it possible to use natural sunlight as a secondary light source. There wasa tank that i heard about somewhere in hollywood that just uses natural sunlight for about half the day. the dude that owns that tank also only has a powerhead and heater running, but no large filtration systems. ab out a 30g tank

 

[mr . salty]

The tank would quickly be over run with algae.Not to mention overheating problems.These are the two main reasons you are NOT supposed to put an aquarium next to a window...