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.

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 - 100W Blue (440-450nm) LED Array: https://a.co/d/4gEHhWZ
2. $10 - 100W Cool White (10,000-15,000K) LED Array: https://a.co/d/4R5cDx6
3. 50W versions exist as well for lower light needs.
4. 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.

Power Supply

1. $55 - 48V variable 480W power supply: https://a.co/d/7ALEe1T
2. 1 can potentially power the whole system.
3. Note: A constant current driver was investigated, but it got very hot (~150F) running nominally, so it was removed and the power supply above became the main driver. Other power supplies and constant current drivers may still be used, just ensure they do not overheat.

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

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.

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.

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 voltage to below 30V before powering on/connecting.
6. Direct the light away from your face and power it on.
7. Increase voltage until it reads 3000mA for 100Watt LEDs (1500mA for 50Watt LEDs)
8. If LED does not light up, check thermal fuse conductivity

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 wood to approximately 6" by 48" (or two pieces 24" long) to be the lighting mount plate(s).
2. Metal could also be used to provide more thermal safety and heat dissipation. A future iteration may switch to metal.
3. Cut the holes 4 inches apart for the lights and 2.125-2.25" in diameter, evenly spaced from the center of the two 24" pieces/halves.
4. Drill screw holes to align with the lens screws for mounting.
5. Attach the light mount plate(s) to two long pieces of wood, each 48" long, on either side.
6. Attach two sheets of wood approximately 8" x 48" to each side of the wood to help block light spillage.
7. While the light directs downward at 60 degrees, there is still significant light spillage beyond that angle, making it harsh to look at without these blockers.
8. Shorter pieces were used in the pictures above due to availability at the time of fabrication.

LED Array Adding

1. For testing and short-term applications, the LED arrays with the heat sink can sit directly in the holes. This allows for testing multiple types of LEDs and placement for the desired effect.
2. For long-term use, it is recommended to bolt the LED arrays in place:
3. Unscrew the lens cover from the LED, but keep it held together.
4. Place the LED array assembly into the hole, aligning the lens fixture holes with the drilled holes in the wood.
5. Screw the assembly together from the bottom.
6. This step can be tricky to align and may require longer screws.

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.

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Simple:

The 48V (480W) variable power supply can run directly in parallel with every LED chosen. Note that if the sum of all LEDs exceeds 480 watts, two power supplies must be used if intending to operate at full power.

1. Note: 480 watts is a lot of power and is sufficient for LPS/soft corals in a 75-gallon tank. The variable power setting on the supply can help adjust the output as needed.
2. Note: The steps below are for the variable 48V 480W power supply listed in the parts list. Some LED arrays from the company use a different voltage—check to ensure the LED array you buy has a voltage of 30-34V. The ones listed above meet this requirement, and most other colors that don’t are not recommended for reef tank applications.

Wiring Steps

1. Connect all wires from each LED in parallel.*
2. If running one wire to the top of the tank for all LEDs, make sure it is a lower gauge sized appropriately.
3. Connect the wires to the power supply.
4. Connect all fans together.
5. Power all fans with a 12V or 9V power supply.
6. While the fans are marked for 12V, 9V will work and provide lower noise, but may not dissapate as much heat quickly.
7. Turn the power supply dial to the left to keep it below voltage during the first power-on.
8. Turn on the power supply.
9. Set the voltage to ~32V.
10. Calculate the maximum amps:
11. Max Amps = (sum of watts of all LEDs) / (supply voltage)
12. Ensure the amps are at or below this value.
13. Adjust as desired to achieve the proper PAR.
14. It is recommended to start at half power/amps and adjust using a PAR meter.
15. Connect the power supply to a timer for automatic on/off control.

*Constant current drivers may also be used. It is recommended to size one for each LED array for safety. Some can be tied in parallel as long as the LED rating is at or higher than the driver rating.

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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 wires from each LED in parallel or split them into separate circuits as desired.
2. One circuit was used for blue lights and one for white in this setup.
3. Connect the wires to the power supply.
4. Connect all fans together.
5. Power all fans with a 12V or 9V power supply.
6. While the fans are marked for 12V, 9V will work and provide lower noise, but may not dissapate as much heat quickly.
7. Turn the power supply dial to the left to keep it below voltage during the first power-on.
8. Turn on the power supply.
9. Set the voltage to ~32V.
10. Calculate the maximum amps:
11. Max Amps = (sum of watts of all LEDs) / (supply voltage)
12. Ensure the amps are at or below this value.
13. Adjust as desired to achieve the proper PAR.

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, adjust the power supply to bring the lighting within range.
6. Ensure you stay below the maximum amp rating of your system.
7. Adjust the placement of the LED arrays as necessary.

Current placement and settings at the time of writing:

1. Placement:
2. 2 × 100W 10,000K cool white fixtures at either end.
3. 2 × 50W 10,000K cool white fixtures on the inside.
4. 2 × 100W blue (440/450nm) fixtures in between the white lights.
5. To avoid blue shadows, the blue lights were placed between the white lights.
6. Midday (8 hours):
7. Blue lights running at half power (50 watts each), driven by 100-watt driver.
8. White lights tied together, running at about 2/3 power (66 watts and 33 watts, respectively).
9. PAR readings (centered on one half of the tank):
10. ~190 PAR (top of rocks).
11. ~110 PAR (sand bed).
12. Morning/Evening (1 hour in the morning, 2 hours in the evening):
13. Blue lights only, running at half power (50 watts each), driven by 100-watt drivers.
14. PAR readings (centered on one half of the tank):
15. ~50 PAR (top of rocks).
16. ~30 PAR (sand bed).
17. While difficult to capture in a picture, the 445nm blue lights create a fluorescent effect with the corals that is quite beautiful to see in person.
18. Maximum PAR
19. Assuming all the LED arrays above are set to 100% output, that would be ~500Watts
20. Based on the measurements the estimated system could get up to around:
21. 310 PAR (top of rocks)
22. 180 PAR (sand bed)
23. To get even higher - the 50Watt LEDs could be replaced with 100Watt and more LED arrays could be added if a higher PAR is needed
24. The current PAR is set lower to fit with the corals in the existing tank

This is a new design, and some potential future upgrades are noted below:

1. Angled Hood Sections:
2. While the flat 90-degree blocks light, an angled hood could help direct some light back onto the tank and reduce the rippling caustics (wave) effects that are a bit prominent with the spotlight created by the point-source LEDs.
3. There are also some blue shadows that sometimes show up due to the spacing between LED lenses and different colored LEDs that may also be solved by this
4. Some reflective tape or aluminum would need to be added to reflect the light back.
5. Another approach could involve using 120-degree lenses while relying on the angled sections to direct the light back onto the tank and disperse the light more evenly.
6. Aluminum Light Mount:
7. To improve safety and thermal heat dissipation, the mount to which the LEDs are fixed is planned to be switched to aluminum.
8. Fans Off at Night:
9. The fans are still a little louder than desired. The plan is to update the code and wiring to tie them into a relay.