Introduction: LED Aquarium Lighting

About: I work as a computer and network technician. Some of my hobbies include woodworking, radio controlled everything, 3d printing and my aquariums.
This is an LED based Aquarium Light. It consists of a sheet of plexiglass with holes drilled in it to accommodate LEDs facing downward into the tank. The circuitry is above the plexi and will be waterproofed with silicone/hot glue later on.  The power supply can be any transformer that you have kicking around. I used a 9.0VDC 800mA clock radio transformer.
The idea of this is to:
1) Reduce the cost of lighting your aquarium
2) Lower the heat generated by lighting

I am in no way responsible if anything goes wrong, and as with any electronics, there is a certain amount of risk involved.

I would not recommend using this on a planted tank because LED's do not have the proper spectrum. 

Step 1: Planning and Design

First off, you must decide how many LEDs you are going to install, and how to install them. I decided to use a 18x3 grid of LEDs. For my 10g tank (20" long), I chose to start the LEDs 1" in from each end of the tank and a 1" space between LEDs. Your design will most likely vary. You also must consider the fact that resistors are needed when working with LEDs. I had this site recommended to me and I found it to be VERY useful. You must know what voltage and current your transformer will put out. You also must have your LEDs chosen and know the voltage and current required by them.

Step 2: Purchasing/Gathering Materials

1) Plexiglass: 1/4" by the dimensions you determined
2) LEDs: I used 5mm white colour
3) Resistors: the ohm rating that you calculated earlier.
4) Transformer: Salvage one from dead electronics
5) Hot glue: a must to waterproof it
6) Thick copper wire: The stuff that is wired in your home

For the plexi I just went to my local glass shop and asked how much a piece of 1/4" plexiglass would be in the dimensions needed. He gave it to me for free, as it was a scrap from another customer. As for the LEDs, I went to ebay and was able to find a great deal for 120 LEDs for about $6 including shipping. For the resistors, ebay was my choice once again and I got 200 resistors (I only needed 18ish) for $5

-Soldering Iron
-Drill Press
-Drill bit the diameter of your LEDs
-Combination Square: OPTIONAL makes it easier to mark plexiglass
-Sandpaper: to smooth off sharp edges
-Something to cut the plexiglass with (I used my bandsaw)

Step 3: Cut Plexiglass to Fit

Now that you have your rough piece of plexiglass, you must cut it to the final dimensions. Leave the paper/plastic coating on the glass until you are totally done!!! I cut mine to about 5.25" wide and 19.5" long. Make sure that it fits snugly on the rim of the tank. As I said before, I cut my plexiglass with my bandsaw, however you can cut it with a knife. Just use the score and snap method. If you do not know how to cut the plexi, look it up.

Step 4: Mark the Plexiglass

Now it is time to mark where to drill the plexiglass. Using the design you created earlier, mark the plexiglass using a pencil. I used a combination square to mark all dimensions, however if you do not own one, you can just measure and sketch the lines. My final design is shown in the sketch below.

Step 5: Drill the Holes for LEDs

Choose your drill bit size and drill the holes. For my 5mm LEDs I used a 13/64" drill bit, however for your LEDs it may be slightly different. Drill slowly and don't force the bit. Peel off the protective plastic and clean up the holes. Sorry for having no pictures.

Step 6: Insert the LEDs

Make sure that all the flat sides of the LEDs face one direction.

Step 7: Solder Rows of LEDs

Side by Side solder the rows of LEDs connecting them in the arrangement you determined earlier. Also solder the resistors in the arrangement you determined earlier. The resistors have no polarity, they can go either way.

Step 8: Solder Main Power Rails

Now it is time to solder the main power rails into the design.

Step 9: Try It Out!

Now it is time to temporarily wrap the transformer power wires onto the main power rails. Don't worry if you plug it in and it doesn't work, just reverse the wires on the power rails and it should work. If it doesn't work, then use a multimeter and check that there is little or no resistance across each joint.

Step 10: Glue LEDs in and Waterproof

Using hot glue, glue all the LEDs in from the top. Apply glue at the base of the LEDs to insulate them. 

NOTE: After about a month of using it and after posting this instructable, I opened up my aquarium hood to find many of the LED and Resistor wires rusting away.  I did not want this to continue, so I coated all exposed wires with hot melt glue.  It took about 15 min to coat everything.

Step 11: Solder Transformer Wires

Solder the transformer wires onto the main power rails.

Step 12: Install the Fixture

Now it is finally time to install the fixture onto the rim of the tank. Make sure that it cannot fall into the water, as this will electrocute your fish. You may have to modify your existing hood to accommodate the new light setup.

Step 13: Enjoy the Improvment

You are finally done and it is time to enjoy the electricity savings and the better light.