LED Aquarium Lighting




About: I work as a computer and network technician. I hold CompTIA certifications A+, Network+ and Security+. Aside from work, I enjoy working on high performance RC cars, my quadcopter and my aquariums. Fav...

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.



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    31 Discussions


    2 years ago

    are you sure only 9V on water resistance (around 10K Ohms =), which is 0.9mA will electrocute your fish:?

    I doubt it :D


    4 years ago on Introduction

    Hello. I know this is quite a few years old, but I am using some 5 & 10mm white, blue, full color and ultraviolet bulbs. Brightness is high to ultra. MCD ratings for the white and blue are 7,000, 8,000 and 28,500. What would you do differently with your project with these bulbs. Radio Shack shutting down enabled me to buy a lot of them for less than a penny apiece. Now i can build my light.


    5 years ago on Introduction

    Hi, thank you for this instructable! It looks like a great project. I am deciding on building something like this vs. high power LEDs but I've heard that these 5mm LEDs don't last as long. I was wondering if you could tell me if your setup is still up and running? Thanks!

    1 reply

    Reply 5 years ago on Introduction

    It was running for about a year. I then changed around my tanks and took it down. When I plugged it in later, there were 2 sets of LED's failed. I did rebuild lighting for a 4' tank with 1w LED's and they were much better. Go with the 1W or 3W LED's, they are all around a better diode.


    7 years ago on Step 13

    I may be replacing the light set up on my marineland eclipse hood, it looks like you're getting more light then what I get with two T5s! Very nice instructable!


    7 years ago on Introduction

    If you get the proper full spectrum LEDs you can use this for planted setups.


    7 years ago on Introduction

    new to building with leds what will happen if you use a transformer from alarm clock and don't use resistors?


    7 years ago on Step 11

    i may sound dumb, but what is a transformer, its purpose, and what kind of transformer are you using?

    1 reply

    A transformer is an electrical component that has two sides (a primary and a secondary). It is used to step a voltage up or down according to the need. His transformer takes the 120 volts AC (alternating current) from the outlet into the primary side and steps it down to 9 volts on the secondary while also converting it to DC (direct current) by additional methods.


    7 years ago on Step 9

    i know that black chord is the power supply...is it plugged directly into the wall outlet? i want to replicate this same concept for my fish tank/turtle aquarium and powering the LED lights is the only part of the project that i am uncertain of.

    1 reply

    A transformer is a device that converts 120V household AC current into usable low voltage DC current. They're usually used to charge electronics.

    So basically the transformer plugs into the wall outlet and provides DC current to power the LED's.  I used one from a clock radio that outputs 9V, but you can use any one that is between ~6-12V.  Just adjust the resistor values for that voltage.


    7 years ago on Introduction

    Great project. I think I will try this at home. Do you think the lighting would benefit from a more diffuse light? I've used thin white plastic before to make LEDs have a more spread out light source. If you had the ability to dim the LEDs, do you think you would? i.e. an adjustable timer (555 timer) would allow you to adjust the duty cycle with a trim pot, or I suppose you could dim them with an additional power consuming pot, but that might not be as efficient. I just wonder if I would ever think they were too bright...

    1 reply

    Reply 7 years ago on Introduction

    As the fixture is, the light is pretty evenly diffused, but using something to make the light more even is a good idea.
    I don't think you would want to dim the LED's.  If you ever wanted to, however, the 555 is the best way to go.  Just connect the 555 output to a transistor that can handle the load of the entire array.  You don't want to use a current limiting pot, they just burn up.

    Another thought is to put some a row of Blue lights in the fixture as well to simulate moon light. You would just have to use a three way switch.


    7 years ago on Introduction

    good instructable! one suggestion - don't use hotglue for this type of stuff - it's not a long term solution...after a year or so in close contact with water it will lose it's bonds and may peel off surfaces. Consider using epoxy or silicone.


    Reply 7 years ago on Introduction

    The internet has a lot of choice. The best electronic shop I've used is mouser. Lots of specs, and lots of choice.


    Reply 8 years ago on Introduction

    Radio shack probably sells them, but you will pay a lot for them.

    Your best bet is to check the yellowpages for electronics shops, specifically stores that sell electronic components.  Just start calling around and ask if they carry individual LED diodes in the colour you want, and if so how much would it be for the number you need.


    8 years ago on Introduction

    can you get the same effect by hot gluing a bunch of throwies into the plexi?