LED Aquarium Light: Custom Spectrum Controller

Custom LED aquarium lighting lets you provide the exact light spectrum your fish and plants need while creating a stunning visual display. Commercial aquarium LEDs are expensive and inflexible, but a DIY build using addressable LEDs or multi-channel LED strips with an Arduino controller costs a fraction and gives you complete control over spectrum, intensity, and timing.

Why Custom LED Aquarium Lighting

• Spectrum control: Match light wavelengths to plant photosynthesis needs
• Day/night simulation: Automatic sunrise, daylight, sunset, and moonlight cycles
• Cost savings: DIY costs 30-50% less than commercial aquarium LED fixtures
• Customisation: Adjust colour balance for planted tanks, reef tanks, or fish-only setups
• Aesthetic flexibility: Create any colour mood for your aquascape

Understanding Light Spectrum for Aquariums

Choosing LED Types

• WS2812B RGBW strip: Good for fish-only tanks where aesthetic colour is priority
• Dedicated grow LEDs: High-power blue + red LEDs for planted tanks
• Multi-channel approach: Separate cool white, warm white, blue, and red strips controlled independently

Building the Light Fixture

1. Mount LEDs on an aluminium channel (heatsink) matching the tank length
2. Space LEDs for even coverage — 120-degree beam angle LEDs work best
3. Mount the channel above the tank on adjustable legs or suspended from above
4. Include a splash guard (clear acrylic sheet) between LEDs and water surface

Arduino PWM Controller Circuit

// 4-channel LED controller
#define CH_WHITE 3  // PWM pin
#define CH_BLUE 5
#define CH_RED 6
#define CH_MOON 9

void setLighting(int white, int blue, int red, int moon) {
  analogWrite(CH_WHITE, white); // 0-255
  analogWrite(CH_BLUE, blue);
  analogWrite(CH_RED, red);
  analogWrite(CH_MOON, moon);
}

Programming Day-Night Light Cycles

Simulate natural light cycles with a DS3231 RTC:

• 6:00 AM: Gradual blue increase (dawn)
• 7:00 AM: White + red ramp up (sunrise)
• 8:00 AM – 6:00 PM: Full spectrum daylight
• 6:00 PM: White + red decrease (sunset)
• 7:00 PM: Blue only (dusk)
• 8:00 PM – 6:00 AM: Dim blue moonlight (optional)

This reduces fish stress and promotes natural behaviour patterns.

Waterproofing the Assembly

• Keep all electronics above the waterline
• Use conformal coating spray on the Arduino board
• Seal wire entry points with aquarium-safe silicone
• Ensure adequate ventilation around the LED heatsink

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