Sorry I forgot about this post. First off 20W Leds would be overkill. If just green for example, all energy is condensed in a single wavelength rather than spread out and filtered. You could likely use a 5W Led and it would outshine a 100W filtered bulb, if not more. Recent advancements in LEDs could improve this further, along with a decent power source. This is an application where you would not use a white LED and filter it.
Second, low voltage.
Third, the colder they are, the brighter. Water makes a nice heatsink.
Fourth, use LiON batteries, timers, and motion sensors. A hobby battery for an RC car or plane may be enough.
Fifth, not too hard to go to an RGB arrangement and get controllable color.
As far as the Bojo, I have no electricity at the pond. A few deep blue LEDs or UV would maybe be enough to draw in bugs, then only turn on the motor for short times once bugs have collected. Battery size for this may be more difficult as I have no idea of the motor requirements.
Maybe after vacation I will put something together and see if it gains traction. Work has been beyond nuts lately sapping my engineering juices.
