I needed a light over my aquarium but it couldn't be a standard florescent or LED fixture because there is no lid on my tank to support it and water drips down from above (so the light needed to be waterproof).
My fish tank has plants growing in it that do not require high intensity light but they started growing much better when I built this light.
My tank is only 10 gallons but this could be scaled up to any size.
This is for my aquaponic wall setup which has its own instructable. To clear up why I keep talking about a wall, check it out here.
Step 1: LED Light Strips
There are tons of cheap, waterproof rolls of LEDs that you can cut to any length and run on 12v. They come in all kinds of colors, or you can pay more for RGB ones that can be set to any color. Cool white wavelengths are supposed to be better than warm white for plant growth. I didn't see a need for color changing ability. They also have differently sized LEDs with different brightnesses, designated by a 4 digit number that is the combined dimensions in millimeters of each rectangular diode (3528, 5050, 5630).
I ordered a roll of 5050 cool white LEDs. They’re about $8 on amazon now. It's 5 meters long and has 300 LEDs total. I also bought a tiny RF controller that is meant for these light strips. It has a remote control that lets you set the brightness and cycle through various strobing modes that are only going to freak the fish out. It's pretty cool and was only $3 but honestly I never use it -- I just keep the lights on at 100% brightness. You will need a controller to use RGB light strips though.
Step 2: Mount on Aluminum
I decided to mount the light strips to 1” aluminum angle.
The metal acts as a heat sink, preventing the LEDs from overheating (although I’m not sure that’s really necessary with these led strips – but you definitely want a heat sink for anything more powerful). And the angle is a perfect shape for shedding dripping water and protecting the electronics underneath like a roof. Plus it will not rust.
A piece of 1”x1” aluminum holds 4 led strips side by side perfectly. Three feet of the aluminum angle was a few dollars at the hardware store. I cut it into two 15.5” lengths with a hacksaw.
Step 3: Wiring
The led strips can be cut and soldered at a spot every three LEDs apart. I cut eight 12” lengths (each with 21 LEDs) and stuck them to the underside of the two aluminum pieces. I soldered the strips together in series with short lengths of wire so that they were connected in a zig zag pattern. I stuck some electrical tape under the ends because I was worried about shorting everything out by soldering to the aluminum.
The first LED strip in the series gets wired to the controller (make sure it’s oriented the right direction) and then to your 12v power source. I had an old ac adapter lying around. I cut off the tip and wired it in. It is 12 volts at 200mA and is more than enough to power the lights. Maybe if I were using a lot more LEDs, I would need to use a power supply with a higher amp output.
Step 4: Waterproof
Afterwards I sealed everything up with some silicone.
When I first made this with only one piece of aluminum and 4 LED strips, I coated all the exposed wiring with a hot glue gun. After a few months I wanted to double the lighting so I took it down to connect a second aluminum strip. I discovered that water had seeped under the hot glue and started to corrode everything. The wires were barely still attached and all of the positive connections had been eaten away to almost nothing! This made it really tricky to repair since there was not much to resolder the wires to.
So now I’m using aquarium silicone which is totally waterproof and will hopefully work much better. I smeared it between each LED strip and on the sides and ends.
Make sure you give the silicone a day to cure before letting water touch it.
Step 5: Mounting (1)
To hang the strips over the tank, I took a plastic coat hanger and cut it in half to make two triangular arms that swing out from the sides of the plant wall.
They are attached loosely with a single nail that lets them swivel up and down so I can lift them out of the way to access the aquarium. The lower part of the arm acts as a backstop, hitting some cabinet supports that prevent the light from falling all the way down.
The top end of the arms are screwed into the sides of the wall (but not too tightly for them to rotate). The bottom ends of the arms have tiny screws in the end to help them catch on the cabinet supports.
Step 6: Mounting (2)
The coat hanger arms attach to the aluminum bars with another pair of nails so you can rotate the lights to whatever angle you prefer. When I had only one piece of aluminum originally, I just glued these nails right into the corner of the aluminum.
But when I added a second piece of aluminum for more light, it needed to hang from the center between the two bars. I ended up using a 3D printer to make two brackets to hold everything level, since my school library has a 3D printer and I always wanted an excuse to try it out.
I made a “M” shaped object in sketchup and had two of them printed by the librarians. They fit perfectly, though very snugly. This was my first time using a 3D printer and I was surprised how smoothly it all went.
One tip when designing tiny objects in Sketchup: build things a thousand times bigger than you intend (1 millimeter = 1 meter) because the program was not meant to deal with such a small scale and ends up being imprecise. When you are done, resize it 1000x smaller.
I attached the Sketchup file here if anyone wants to use or modify it.
Step 7: Connectors
I actually wanted the light to be removable from the power supply (which was hidden inside the cabinet under the fish tank) so I used USB cables as a connection.
I got an old front facing USB/headphone port from a trashed computer tower and wired two of the USB ports to the 12 AC adapter (using the red wire for + and the white wire for -, and ignoring the other two in USB cables).
I drilled a hole in the side of the cabinet, which allowed me to use a jigsaw to cut a square hole and mount the USB hub in there, facing out.
I connected the wires coming off the LEDs to an old USB cable (again using the red wire for + and white for -). Now I can just plug in anything that has a USB connector and needs a 12v power supply to this hub. If I decide to make more lights in the future or maybe attach a computer fan, the multiple ports will come in handy.
Step 8: Results
That's it. Plug the 12v power supply into a timer and forget about it.
For a few months I used only half of what you see in the pictures: one aluminum piece with 4 led strips containing 84 LEDs. It was a little underpowered and I doubled it with a second piece of aluminum angle and 84 more LEDs. There was a major growth spurt on some of the plants after that.
If you have a serious planted tank with demanding plants and injected CO2 and fertilizers, you'll probably need more powerful LEDs.
Check out the whole aquaponic setup at this instructable!