One Fish, Two Fish
Red Fish, Blue Fish
   - Dr. Seuss

Decorate your aquarium with NeoPixels. Add a high density strip of lights above the water for a beautiful overall colored glow, with subtle color shifts and changes. Cycle between color modes to suit your mood, the time of day, or to signal feeding time. 

For an extra special bit of underwater magic, attach a NeoPixel Strand and submerse the lights under the water. Diffuse the lights with seashells or bits of colored glass to complete the effect. 

This DIY solution will cost you a lot less than the prepackaged aquarium LED light kits available at the pet store, and will give you a lot more control over brightness, color modes and customization. But it's the addition of the submersible strand that really makes this project special, and will make your aquarium stand out from the crowd. 

My aquarium features Tetra fish that have been genetically bred so that their scales fluoresce and glow under blue lights. It's fun to play around with the NeoPixel's hue and saturation to find the color spectrum that makes their colors really shine.

Parts Needed

Microcontroller

We're using the adorable QT Py microcontroller. It's inexpensive and easy to use, and small enough to fit into a projects with limited space.

Lights

NeoPixel LED dots are rugged and robust, and submersible underwater so long as the ends and connectors are sealed up. They're easy to hide under seashells or glass beads and are really what make this project special.

This project also features indirect lighting from above-water lights to illuminate the entire tank and make the water appear to glow. These 144/meter lights will offer the smoothest animation and color shifting because of their deliciously high density. If you're on a budget, the 30/m or 60/m NeoPixels can work just about as well.

Additional BIts & Pieces

This build uses JST connectors between the light strips and the QT Py microcontroller, to make reprogramming your lights easier. It can be tricky to move an aquarium once it's set up, so making the QT Py easily removable is a good idea in case you ever want to update the code and give your fish something new to look at.

This also makes the submersible light strand easy to swap out in case your waterproofing isn't quite up to long term submersion.

The code has 6 different color modes you can cycle through to suit your mood, as well as a software on/off brightness toggle. These features are triggered by touching a length of copper tape connected to the QT Py's onboard capacitive touch pads. Adafruit carries copper tape with a conductive adhesive on the back, making it ideal for use as a stylish and steampunk-style capacitive touch switch. 

Whenever working with electronics and water, it's a good idea to have a quick way to turn your whole system off in case of splashes or shorts. This on/off switch plugs inline with your USB cable for a no-fuss off switch. 

Also grab a USB C cable for programming and powering the QT Py.

Tools & Accessories

This list may vary depending on your build environment, but these are all useful things to have ready.

• Solder-seal wire connectors
• 3/4" cable staples and a hammer for installation
• Hot glue gun
• Heat gun
• Soldering iron & accessories
• Aquarium gravel - fluorescent colors are available! Shop around.
• Colored glass, sea shells, and plants or plastic plants made for aquariums