I am in constant implementation of LED's & i just love them. Aquarium is a great place i started with where i do lots of experiments not just LED's but rest too.
There are plenty of aquarium lighting ibles available including those are which includes plexi glass and hooking plenty of LEDs to get the effect and trust me they look good and plenty of time too and more probability of messing and maintenance ,moonlight is my favorite.
What this ible shows the same with less amount of hard-work :P
NOTE : am extremely sorry for low resolution pics and video since am out of town and this is what i have in my dropbox. The effect is more visible in actuality.
This is the final output
Step 1: Requirements
1Watt LED (BLUE) x 2
1Watt LED (RED) x 2
(reason for choosing these two colors cause these give extremely nice purplish color which enhances Fish and ornaments color)
2> AC-DC Adapter
3> Connecting Wires
Plexi glass (optional)
(these are optional since designed can be tweaked to greater extent suiting ones needs)