Reef Tank LED Lighting High PAR - Low Cost DIY

With the cost of reef tank parts being so high, in many cases, it is more economical and rewarding to build parts of a system oneself. Proper lighting for a reef tank can run as high as 4-8 watts per gallon to keep coral growing (reference). For a 75-gallon tank like the one pictured, that is 300-600 watts. Modern reef lighting solutions can be $800 per light section and only provide 135 watts, meaning a reef for a 75-gallon aquarium would require 2 or more to grow a reef, costing $1,600 or more (depending on lighting requirements for SPS vs. LPS/soft type corals).

Now, watts are just used as a rule of thumb or ballpark before testing the real metric, PAR. The LED colors chosen (high Kelvin & blue LEDs), coupled with lenses that direct light to the aquarium, will lead to high PAR at minimum power consumption. However, with LED solutions still being so expensive, previous T5 or metal halide solutions may still be in the running. Nonetheless, the efficiency gained by LEDs far outweighs the upfront costs. Even the expensive modern LED lighting solutions will likely beat the power, replacement, and other costs associated with metal halide or T5.

Therefore, this guide aims to broach a DIY solution as a low-cost alternative that rivals modern solutions and is an improvement over metal halide and T5.

Personal Note: At the time of writing this, I have had this reef tank for about 2.5 years. I am an avid DIYer and have even built the stand for the tank myself: https://ryanogilvie.weebly.com/woodworking.html. I am constantly learning and improving this tank, but always trying to stay on a budget as best as possible. I have built previous lighting solutions for the tank, with this one being the 3rd iteration. The second iteration used strip lights from Amazon on a sheet of aluminum and worked well enough to grow my LPS & soft corals. However, it was always limited on output and threw light everywhere around the room. This project began as a way to increase PAR for my fish tank after finding these LEDs available online.

Update (6/2/25): Reworked fixture to add UV and red LEDs, aluminum plate on the bottom, 3D printed cover, and diffusion screen

Difficulty: Medium

Skills Required: Basic Shop Skills, Electronics/Wiring, Programming (Optional)

Note: This is a prototype that will likely be iterated on and updated. This guide is intended to provide ideas for building your own but not copied exactly.

Safety Note: LED power required to light a fish tank has to mimic the sun. As such, LEDs included are high power, hot, and blinding. Thus, building this can be dangerous—be very careful when attempting to build this and do not attempt it if uncomfortable.

Disclaimer: Reader accepts all risks with building this. The author assumes no responsibility for any damages that may occur from building/using this device.

Costs rounded & listed for reference at time of posting: 1/20/25

Thermal Management & Lens

1. $24 - Heat Sink 60-degree lens: https://a.co/d/ffT0epE
2. Also comes as a 120-degree lens if you need to mount closer to the tank.
3. $7 - 10 x Thermal fuses set for 77°C (https://a.co/d/1Fl6hnO)

Light Options

1. $10 - 50W Blue (460nm - 470nm) LED Array: https://a.co/d/5KJH4ou
2. $10 - 100W Cool White (10,000 - 15,000K) LED Array: https://a.co/d/4R5cDx6
3. $20 - 50W Deep Red (650nm - 660nm) LED Array: https://a.co/d/2iLemQV
4. $25 - 50W UV (425nm) LED Array: https://a.co/d/3Xx32Zm
5. $10 - 50W grow light (380nm - 840nm) for sump https://a.co/d/d7AC6mI
6. 50W +100W versions exist as well for lower or higher light needs.
7. The links above also provide other color options, such as light blue (460-470nm), lower Kelvin white, and other options that could be worth exploring.
8. $15 - Light diffuser: https://a.co/d/0CkU2b0

Power Supply

1. $55 - 48V variable voltage/current 480W power supply: https://a.co/d/8BqBsLO
2. 1 can potentially power the whole system.
3. $20 - 1500mA constant current power supply: https://a.co/d/6J1P1Dy
4. Powers a 50W Array or 2 at half power etc...
5. $36 - 3000mA constant current power supply: https://a.co/d/iPnNi60
6. Powers a 100w array or 2 at half power etc...
7. This particular one gets hot (~150F) so ensure you mount it on a safe surface.
8. Note: different current drivers can be found on the links above for higher or lower light needs.
9. Note: while the same and select colors operate on the same/similiar voltage, UV and red operate at different voltages and must have dedicated drivers

Electrical Control

1. $32 - Arduino Feather M0 with Wi-Fi: https://a.co/d/grIE2OJ
2. $10 - 8-channel relay module: https://a.co/d/cyoczXg
3. 9V or 12V power supply

PAR Measurement/Verification

1. $150 - PAR meter: https://a.co/d/iUFqytN
2. While not required to build this, it is critical that any reef keeper have one. It is essential to verify the output is sufficient (or too high) to grow coral.
3. This is a budget PAR meter I use—there are more options out there if desired.

Wood & Metal for Structure

1. Local Hardware Store

Determine Total Watts

Using 4-8 watts per gallon as a rule of thumb, multiply by gallons in the display tank. For my case that is 75gallons so 300-600watts. I went with 400watts.

Determine Colors

Using the chart above: https://orphek.com/correct-corals-spectral-needs/ and the chart from https://www.reef2reef.com/threads/lighting-spectra-photosynthesis-and-you.100170/ you want to maximize chlorophyll A, cholorophyll c, and Cartenoids, with the majority focus on chlorophyll A as it outnumbers C 10 to 1. They are not typically know to use chlorophyll b and f. Therefore the best additions are in the 400-500range range and the 660nm range. 425nm, 465nm and 655nm were chosen in addition to 10,000-15,000K white lights. The white light is intended to fill in everything in between as you can see in the graph above for 10,000 and 20,000 white lights: https://www.reef2reef.com/threads/20000k-and-30000k-led-spectrum.725445/#post-7543880, though the focus in on the blue lights and the red light. Indiviuals may adjust as desired to try different amounts for their setup.

Current setup:

1. 2 blue (465nm) at ~100W total
2. 4 white (ranged see chart above) at ~ 150W total
3. 2 UV (425nm) at ~100W total
4. 2 red (655nm) at ~50W total

While this is a start, make sure to verify PAR is sufficient for your corals at the final step

The first step is building the LED modules. Based on the number desired for the size of the tank and type of corals, this process will be replicated as needed. Shown is for one LED array straight on a heat sink for illustration.

These high-power LED arrays require a heat sink to function; otherwise, they will overheat and burn out.

Assembly:

1. Solder the wires onto the LED array, going through the holes from behind. The wires need to be kept below the surface of the LED as much as possible to prevent interference with the lens assembly and ensure proper fit.
2. 22-gauge aluminum stranded wires were used in this application.
3. Apply thermal paste to the heat sink.
4. Screw the LED array onto the heat sink using the provided screws. Route the wires through the provided channels on the heat sink.
5. Clean the LED array with IPA and microfiber cloth, ensure you remove any dirt or imperfections that could overheat and damage the surface during operation
6. Screw the lens on top of the LED array. Check to make sure the lens is not floating; if it is, tighten the screws further.
7. Super glue/epoxy thermal fuse near top of LED heat sink as shown
8. In case a fan ever fails, the LED array will likely overheat, potentially damaging the LED or creating a fire hazard. A thermal fuse will kill the LED array before it gets to this point.
9. Cut one LED wire with just enough to connect to thermal fuse
10. Add heat shrink to both ends
11. Solder cut wire onto both thermal fuse ends to close circuit
12. Complete quickly to avoid accidently killing the fuse, do not cut the fuse ends too short to help avoid this
13. Put heatshrink in place and apply heat with a heat gun

Testing:

Safety Note: Do not look directly at the light, as it can blind you from extended viewing.

1. Connect the fan to a 12V or 9V power supply.
2. 9V was used in this case to make the fan quieter.
3. Ensure the fan is running during any extended periods of operation.
4. Connect the LED to the power supply or driver.
5. Set current to 0 before powering on/connecting. Set Voltage to ~34V
6. Direct the light away from your face and power it on.
7. Increase current until it reads 3000mA for 100Watt LEDs (1500mA for 50Watt LEDs)
8. If LED does not light up, check thermal fuse conductivity

Similiar to the steps above the LED arracy can be coupled onto an alumium plate to combine more than one LED array with a single heat sink. Make sure you use aluminum for the heat trasnfer properties. The aluminum can be drilled to mount the LED arrays on one side an heat sink on the other side. Similiar to the process above add thermal paste for each connection.

The light fixture described above is a basic design to hold the LED arrays and heat sinks and hang from the ceiling. There are many different iterations and styles that could be used, but the following steps are provided as a general guideline to replicate this design for a 75-gallon tank.

Fixture Construction

1. Cut a sheet of aluminum to approximately 6" by 48" (or two pieces 24" long) to be the lighting mount plate(s).
2. Cut the holes for the lights and heat sinks
3. Drill screw holes to align with the lens screws for mounting.
4. Attach the light mount plate(s) to two long pieces of wood, each 48" long, on either side.
5. Attach the LED arrays and heat sinks to the plates as desribed in the step above.
6. Create a cover for lights to keep it from spilling around.
7. A 3D printed cover was designed for this. Spray painted with mirror spray on the inside to help light focus downward and added a diffuser on the bottom using heat inserts to bolt it in place. Light shade 3d print STL is attached.
8. As a simpler solution some pieces of wood could be mounted to the wood spars holdings the bottom plates

Hanging

1. Add four hangers, two at either end of the fixture.
2. Mount ceiling hooks.
3. Run a metal chain through the hooks and hang the assembly.

To control the lights, there are simple and advanced options. The advanced option is intended for those with decent electronics and programming skills already; this guide does not go into the details of how to program. The pictures above with the controller illustrate the advanced option.

___________________________

Simple:

Wire each LED to a constant current driver. It is recommended to size one for each LED array color type for safety. Keep driver below or at combined rating of the LED arrays. Some colors may be able to be tied together if they have similiar voltage and testing.

Wiring Steps

1. Connect all drivers to LED arrays
2. Connect all fans together.
3. Power all fans with a 12V or 9V power supply.
4. While the fans are marked for 12V, 9V will work and provide lower noise, but may not dissapate as much heat quickly.
5. Plug in drivers into the wall power and test output.
6. Any combination of the drivers may be combined into one 120V circuit as desired
7. Connect drivers to a timer for automatic on/off control.

___________________________

Advanced:

The steps and software below are intended for an Adafruit Arduino Feather M0 that connects to Wi-Fi to keep time updated for control. It connects to a relay module that can handle the high currents used by the lights. While the standard mode automatically uses time to control the relays, there are switches to set it to manual mode for after-hours use when the lights need to be on for any reason.

1. Note: A secondary feature in the code refills the tank with a solenoid to avoid accidental overfill. The tank is hooked directly into an RODI supply system pressurized by the local water supply. While a float valve is a great option for auto top-off, it could fail. A secondary electric system allows it to refill for 30 minutes a day with a solenoid, enough to catch a failure before it becomes a problem. Coupled with the float valve, this provides a fault-tolerant system in case either one fails. - I may write a detailed guide on this if there is interest

Processor Relay Setup:

1. Mount the processor onto a board and connect control lines to the relay module according to the pins/code below.
2. Power and ground the relay module.
3. Wire up a manual/auto switch and a manual option button switch as desired.
4. Ground the control pins with a resistor to avoid floating ground.
5. Provide power to the processor.
6. A 9V-to-5V converter was used to power the processor using the existing fan's 9V power supply.
7. Program the processor using the code below.
8. Modify the code as desired or to fit your processor.
9. Remove the refill code if desired, or leave it in—it will not affect operation unless you need to use that pin/relay.
10. Add a connection to your home Wi-Fi network.
11. Test the operation without lights to verify the relays work as expected.

Wiring/Power Supply Setup:

1. Connect all drivers to LED arrays
2. Wire through the relay module for each circuit
3. Connect all fans together.
4. Power all fans with a 12V or 9V power supply.
5. While the fans are marked for 12V, 9V will work and provide lower noise, but may not dissapate as much heat quickly.
6. Plug in drivers into the wall power and test output.
7. Any combination of the drivers may be combined into one 120V circuit as desired
8. Connect drivers to a timer for automatic on/off control.

Integration:

1. Connect the relays in line with the lighting circuit(s).
2. One circuit was used for blue lights and one for white in this setup. These can be adjusted as needed.
3. Test the lighting to ensure it works with the relay circuits.

Once the lights are hooked up, check the PAR using a PAR meter. As a general rule of thumb, soft/LPS corals require 50–150 PAR, while hard stony SPS corals require 200–500 PAR (reference).

1. Determine the PAR range based on the corals you have.
2. Obtain a PAR meter and turn it on.
3. Remove the cover from one side of the tank. Leave the cover on the side you intend to measure, if possible, to account for any attenuation caused by the cover.
4. Measure PAR:
5. If PAR is too high or too low, swap out with higher or lower drivers and LED arrays
6. Adjust the placement of the LED arrays as necessary.

To avoid blue or colored shadows, white lights were places on the outside.

To reduce shimmer (light scattering) a diffuser was added.

PAR - tested

Assuming all the LED arrays in the sizing section, that would be ~500Watts

The 75 gallong system shown could get up to around:

1. 310 PAR (top of rocks)
2. 180 PAR (sand bed)

For the sump tank a full spectrum LED array setup was put together to grow algae and reduce Nitrates. A single LED array setup for growing plants was used (380nm - 840nm) at 50W. It turns on for about 8 hours a night. A 3D printed Cover was created and spray painted with mirror spray paint. Also a 3D printed holder was made to mount it to the ceiling with holes for the fan for cooling. These are attached.

A previous edition just used wood and had a couple white and blue LEDs in line. This could be a simpler implementation, using single modules than an integrated approach, but lacks heat dissapation on the aluminum plate, extra UV and red lights, and a diffision screen.

For testing and short-term applications, the LED arrays with the heat sink can sit directly in the holes with this application. This allows for testing multiple types of LEDs and placement for the desired effect.