[jeffkrol]

Think about the beam angle like this.

Here is a 90* angle. /-------\ obviously more coverage if you have it directly on the tank. If you hand it however more light will be shot over the tank instead of in the tank.

Yes and no.. or it depends..
You can lose light and gain coverage.. There are many factors in play..

 

[jeffkrol]

True for any light.

It is probably less true for LED's since you'd just swap out lenses.. say go w/ a 60 degree to refocus .. yes you lose some for the inverse square rule but you are also refocusing..

http://sdhydroponics.com/resources/articles/gardening/inverse-square-law-for-light