Choosing LED light for reef tank – Beginner guide
It was quite easy to light a tank with T5 neon bulbs. You had to choose between some colors, mix them to have the color temperature you liked and that was it.
LED fixtures changed everything, and it is now more difficult to choose between all options.
We will see here some criteria to take into accounts to choose the LED fixture for your reef tank.
LED technology changed the way we light up our tanks
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Size and type of fixture
Whereas you only had to choose T5 length to suit to your tank, and the number to cover the whole surface of your tank, you now have the choice between several kind of high-power LED fixtures.
LED Clusters / Pads
LEDs are very small electronical components. Fixtures with them are more discrete than big T5 fixtures. With technical improvements, it has been possible to create smaller and smaller LED cells and regroup them into clusters, concentrating high light power in small devices.
Extreme light power comes from only few centimetres now.
LEDs have single color emission, so grouping them allow a better color mixing. Using several kinds of blue LEDS, whites, green, red improve corals coloration and growth, without seeing a rainbow light effect over the tank.
Optical lenses are used to improve light spreading and color mixing. According to their diffusion angle, they spread widely light or concentrate it. A 30×15 cm LED fixture can be sufficient to light up a 60 x 60 cm area for example or can have great light penetration on water column of a smaller area with narrower diffusion angle.
Maxspect RSX has its LEDS in pads.
Concentrating LEDs into clusters leads to concentrating the whole light power into cones under them. It is necessary to multiply fixtures over big tanks to light up the whole area and to reduce shady spots.
Fixtures with individual LEDs on their surface
Aquarium Systems Series 6 has its LEDs spread 3 by 3 on the whole surface.
Here, fixtures are generally bigger. All diodes are spread over the surface. It has for advantage to better spread the light and avoid shady spots. But light power is locally lower than under clusters. According to the diffusion angle of lenses, color mixing can be less effective, and you may see some color zonation.
Philips Coralcare has its LEDs on almost the whole surface.
Finally, according to the power of single diodes composing the fixture, they can be limiting for higher tanks.
LED bars
Bars are trendier today than some years ago. They can be used as complement for clusters/spots fixtures, but also as main light sources by adding several on the tank’s width like we did with T5 neon bulbs.
Lancia LED Bars
Their advantage: they light up the whole tank’s length. Their inconvenient: they light up on a narrow width.
Also, like the fixtures with several diodes spread over their surface, a “rainbow” effect can appear if the optical lenses concentrate too much the light. In this case, you can see the different LED colors along the length of the ramp.
Spots
This is the last main fixtures we can find on the market. They are made of one unique cluster, concentrating all the power on one spot and spreading the light narrower or wider according to its optical lenses.
Spots are convenient on square tanks and deep tanks. The concentration of light makes it go deeper in the height of the tank. But be careful to not burn the corals at the surface. You can adjust the spot’s height and dim the power.
On rectangular tanks, you can use several of them and add bars for example.
Schematic diffusion cones under each kind of fixture.
Power
Relative intensity diffusion under each kind of fixture- Shady spots are to take into account.
Besides the type of fixture, its power is also a determining factor. Brands’ recommendations are nowadays not so far from reality. You can lower them a bit to be sure to have enough power for most demanding corals, but it is generally the light spread/covered area that is limiting. You must consider the size of the tank, the hardscape, the height you setup the fixture and the corals you want to keep. If a fixture is sold to light up a 60×60 cm, you can consider it for 50×50 or 60×50 cm for example, and it will be fine.
Total power is generally not limiting. And if it is the case, it is mostly a matter of LEDs composition. Blues and whites LEDs bring most of the energy corals need. If greens, red, amber, ultraviolet are too numerous, taking a too big part of the total power, in this case, power can be limiting.
When it is about power, we generally think at total power of the fixture. But the power of each individual LED composing it is also important. LED fixtures for reef tanks are usually composed of 0,5 to 5W LEDs. But 10 LEDS of 0,5W do not produce the same light as one 5W LED. Lower power LEDs’ light penetrates less in the water column. They are sufficient for shallow tanks for example.
LED composition
Corals are the result of a symbiotic relationship between a “jellyfish”, attached to its substrate (we call it the polyp), and unicellular algae (zooxanthellae). And who says algae, says light is needed. They produce pigments which are proteins absorbing light and using it as energy source for their metabolism. But each kind of pigment does not absorb light the same way. Chlorophylls, major pigments, absorb most of the violet and blue light. Fluorescent pigments are also activated by this light colors. Other accessory pigments enlarge the absorption spectrum of corals. Photosynthesis, the metabolic activity of plants and algae, is activated by two receptors reacting at red light (680 and 700 nanometers).
Red Sea plays the easy setup card with their ReefLED : one blue channel, one white channel and moonlight.
Knowing this, we must mainly focus on blue and white LEDs. From our experience, it is possible to find a good spectrum for corals with fixtures displaying 1,5 to 3 times more blue power than white light. You can then adjust the ratio to have more blueish or warm light.
Violet, ultraviolet and cyan LEDs stimulate fluorescent pigments production and effectively increase energy absorbed by corals. They increase corals coloration and growth for demanding corals. Their presence in the composition is a “true plus”.
Other colors must be secondary in the total power of the fixture. They complete the visual color rendering of corals.
Other features
Many features are proposed on some LED fixtures.
You can create daily programs with each LED color intensity on mobile app.
The main ones are wireless (wifi/bluetooth) connection and dimming. Dimming is important, as it allows to create an ideal spectrum for your tank. Without wireless connectivity, you can do it thanks to a built-in screen or external controller. Mobile app makes it easier. You can also setup sunrise and sunset.
On more basic models, you have to manually switch ON/OFF the light, or put it on a “clock socket” programmer. Some fixtures also have a simple switch allowing you to adjust 2 channels ratio (blue/white).
Other features like storm, clouds, lunar simulation must not be a decisive factor in your choice. Lunar light simulation is the most interesting, reducing fish stress and improving natural cycles stimulation.
No brands / copycats or well-known brands?
Today we can easily buy products from anywhere online. We find very cheap models, without brands, directly from manufacturers. Whereas some are really low quality, others are real lookalikes. 2 or 3 times cheaper than the branded models, the hesitation is real.
Basic components of LED fixture. Are they all of the same quality in high-end and cheap models ?
Note: Of course, some brands outsource their lights fabrication. But they generally impose the technical specifications, using higher quality components and have serious quality tests.
Really cheap/bad quality models are made of bad quality and low power LEDs, with bad blue/white ratio. Rendering is bad. They can do the work for small tanks / low demanding corals. Heat sinking is also insufficient, and high temperature is critical for LEDs longevity.
For copycats, it is important to take into accounts:
- The quality of components. There are several LEDs manufacturers, with various quality standards and not using the same raw material. It ends to lower luminous output at equal or higher power consumption. Also, products lifetime can be tricky. With bad heatsink, LEDs overheat and die. Does the lookalike manufacturer use the good passive heatsink and does he use heatsink paste/glue? Using low quality diodes also leads to different spectrum.
- The Customer Service. It is easy to get spare parts and/or replacement fixture when a problem appears with a renowned brand during warranty, especially when you have a local fish store that sells the brand next to your place. Whereas we can generally forget any customer service with products bought on marketplaces.
It is of course possible to get a nice reeftank using these lights. But lifetime/warranty can be tricky.
In a nutshell
To choose your LED fixture:
- First, take a model which size/type corresponds to your tank, and take the good amount according to the advice of the brand (you can underestimate them a bit) to cover your tank.
- Be sure to have a good blue/white ratio. 1,5 to 3 more power of blues allows you to create nice spectrum and have colorful corals.
- Several kinds of blues and violets make the corals fluorescence pop and extra growth on high demanding corals. Other colors are extra.
- Wireless connectivity and dimming are almost obligatory. Other features are not necessary.
