High-end LEDs promise to deliver the right light to the right place. But how much of it makes it to the bottom of a tank after water gets in the way? Gabor Horvath investigates.
In many cases, the purpose of aquarium lighting is for the enjoyment of the fishkeeper. Many fish we keep come from rainforest streams shadowed by the trees, and for them even ambient room light is ample. We can even stress some species by offering them too much light.
Aquariums with artificial or undemanding plants can do well with subdued illumination, so for Anubias, Java fern, Lomariopsis or even Cryptocoryne, you don’t need an expensive light. Most of the tanks in my fish-house have these plants and are adequately illuminated with affordable low-performance LED lamps. Only those wanting to keep light-hungry plants or high-tech aquascapes should turn their attention towards more powerful light units.
Understanding the real (practical) meaning of various measurements of light output is a key to the success. The brightness of the lights is usually expressed in ‘lumens’ or in ‘lux’. Lumen refers to the amount of light emitted by the lamps, while lux shows the amount of light falling to a certain area (the amount of lumens over 1m2). In aquaria this latter is the more useful measurement; lux value changes with depth and light angle, so it provides an accurate value of light actually reaching your plants.
For the aquarium, it’s not only the quantity of the light that counts, but also the quality. White light is made up of a broad spectrum of different wavelengths, while plants and corals require very specific regions of the wavelength that contain PAR — Photosynthetically Active Radiation.
A PAR meter measures the light’s relevant ‘strength’ for plant growth as it directly measures the amount of light available for plant photosynthesis (as millimoles of light energy per square meter), therefore it’s more meaningful than the lux alone.
Put into layman’s terms, for undemanding plants 20-30 PAR would suffice, but you need around 50-60 PAR for the majority of the plants. For red coloured and other light-intensive plants you may need over 90 PAR. In marine tanks, soft corals and LPS corals need 50-150 PAR, while for stony and SPS corals 200-500 PAR is required.
Marine tanks require higher PAR levels.
Which light for which organism
Plants and corals use chlorophyll and other pigments to absorb light for photosynthesis. There are five types of chlorophylls, with ‘a’ and ‘b’ being the most important.
These pigments can only utilise certain wavelengths from the spectrum, including wavelengths of blue (430-475nm) and orange-red (630-675nm) light.
Freshwater plants tend to live in relatively shallow water and have access to the full spectrum of light, and an optimal light for them should produce light in those ranges.
These wavelengths alone may maximise plant growth, but your fish and tank would look unnatural in the resulting cyan-magenta light, so aquariums require something more balanced.
Retrofit aquarium lamps with white LEDs can produce relatively intense illumination, but their spectrum often contains little light that’s useful for photosynthesis. But they’re suitable for undemanding plants and at around £30-£60/light for a 120cm aquarium, perfect as a budget choice.
One level up we find luminaires using RGB (Red-Green-Blue) LEDs, with opportunities to adjust the colour or the strength of the light. These ‘strip’ lights were mainly designed to replace existing light units, but some come with a hanging kit for use as a pendant lamp. The more advanced versions — let’s call them ‘prosumer’ lights — offer enhanced programmability. The price reflects what they offer. and they will set you back between £100 to £300. You’ll find many products in this category, including JBL, Fluval, Aquarium Systems, Juwel and Eheim. They’re great performers in most situations, but when it comes to high-tech aquascaped planted tanks, lights specifically designed for them are more often used instead.
In marine tanks the requirements are quite different. Corals need stronger lights, with Small Polyp Stony corals from shallow seas being the light-hungriest. They get a full dose of sunshine in nature and require full spectrum lighting- including reds.
Other coral species live deeper, where limited (if any) red light is available due to the light absorption of the sea water. Creatures from the deep blue are well adapted to use the blue end of the spectrum, which is why marine lamps are strongly biased towards blue.
Freshwater habitats may be shadowed by plants.
Why choose a high-end light?
A pitch often cited for high-end lighting is that ‘ordinary’ lights lack the penetration required to reach the bottom of a deep aquarium. According to the Inverse Square Law of light, the light intensity decreases inversely proportional to the square of the distance to the light source. This law applies to every single light, low-end and high-end alike.
The differentiating factor is the initial power and the concentration of the light beam. Generic lights are mainly designed for replacing existing lamps and sit close to the water’s surface (at 5-10cm). They usually produce a relatively wide-angle light to provide even lighting at close distance. The downside of this spread is that less light gets down to the bottom of the tank.
When using such lights around 20-30cm above the water level, the additional light loss can lead to insufficient lighting at substrate level. High-end lights are powerful enough to cope with this extra distance, providing a narrower, stronger beam of light.
They also suffer from light fall-off, but they pack enough punch for plants or corals growing on or near to the bottom.
Another pitch is that high-end lights can provide more balanced lighting. Every high-specification light today comes with some kind of controller or Bluetooth/Wi-fi connection to allow you to fiddle with your lighting. You will find similar functions in many ‘prosumer’ lights, but while those only allow you to adjust the white and RGB (Red-Green-Blue) channels, high-end lights usually offer six or eight channel control, meaning that you could fine tune your lights to the perfect spectrum required. It also partly explains why high-end units are more expensive: they use a range of coloured special LEDs instead of the readily available cheaper RGB ones to get as close to the natural lights as possible. Some of them even have UV LED’s.
SPS corals receive intense light.
How were they tested?
I was interested to see whether I could really find differences in the performances of ‘everyday’ and ‘high-end’ units.
To represent the first group, I picked lights I have been using in my fish house for a while: an AquaEl Leddy Slim and two Aquarium Systems Proten Gen 2 lights (Freshwater and Marine). The other end was represented by the AS S6-60 and two brand new lights — a Twinstar 600SA III and a Life Aqua Prime in the freshwater category — and by a ‘vintage’ Phillips Coral Care and a recently released TMC Reef Pulsar LPS-6 for marine use.
The lights were tested in a long-established 50cm tall tank to measure the real-life performance. The measurements were taken by using a Seneye Spectra, a great tool for those wanting to know everything about their lighting. The Spectra displays the spectrum of the light, the PAR values, and calculates the PUR (Photosynthetic Usable Radiation) values based on the types of plants or corals you keep.
The Spectra sensor was attached to the end of a stick long enough to reach the bottom of the tank, while the lights were fixed 30cm above the water level to represent the usual positioning of pendant-type lamps. The only difference was that I placed them across the width of the aquarium (as opposed to the length), so that I could measure the light coverage up to 50cm off-centre. Every light was turned up to maximum power.
After a short warm-up period, PAR measurements were taken at 20cm (10 cm above water surface) distance and at 0cm, 10cm,20cm, 30cm and 50cm depths right under the centre of each light, as well as 10cm, 20cm, 30cm and 40cm off-centre at each depth. I also measured the PAR at 100cm distance from the luminaires outside of the tank.
The results prove that regardless to the type of the lamp, light fall-off applies. Between 20cm and 60cm distance from source, every single light lost 70-80% of its PAR intensity. The big difference was that due to their initial high power the top lights still had enough remaining power at 80cm (meaning the bottom of the 50cm deep tank) to provide sufficient lighting.
The light spread
The spread values show how the various lamps project the light under the surface. I took the PAR measured at the water surface right under the lights as 100% and mapped the other values on a graph.
The diagram of the AquaEl Leddy Slim shows that it spreads the light, resulting in over 80% intensity even at 20cm off-centre. This drops to 40% in the same position 10cm deeper, while the centre is still 70%. At 30cm depth the performance levels up, staying around 25% (of the value measured at the surface) throughout the area.
As opposed to this, the Life Aqua Prime concentrates the light much more tightly for deep penetration. It consistently provides the same amount of light (40-55%) throughout the 10-30cm depth range even at 30cm off-centre.
The TMC Reef Pulsar also provides evenly-spread light especially below 30cm depth, ensuring that every coral there receives the same amount. Although only 15% of the surface value gets down to 50cm (a total of 80cm distance from the lamp) it’s still more than enough for the majority of the LPS corals.
As discussed earlier the amount of light produced itself doesn’t make a lamp excellent. The light should contain all the essential wavelengths without wasting energy on producing useless ones. The colour spectrum of the TMC Reef Pulsar LPS-6 is an example of how well adapted high-end lamps could be. It almost perfectly matches the optimal light spectrum required by deep water corals: a range of blues with minimal reds.
Life Aqua Prime
This light has just appeared on the market but is already receiving praise. It has a passive cooling system, making no noise during operation. The Cree RGB LEDs are embedded in 90-degree reflectors, which keeps the light beam between the walls of the aquarium (not blinding the viewer) and provides good light penetration, and the optics provide a great shimmer effect. With the Pro version there’s a 3 channel (plus UV) control and full programmability. It has everything you would expect from a great light and only consumes 32W.
Twinstar 600SA III
This is the third generation of these much-loved lights. The S-line has become famous for making plant colours stand out and the new 600SA continues this tradition but adds even more power with a minimalist design. The only downside is the lack of a control software (you could get an optional timer-dimmer with sunset and sunrise function), but because the lamp has a perfect spectrum straight out of the box why bother? It’s an affordable light for those wanting a high-end luminaire without breaking the bank.
Aquarium Systems Series 6 S6-60
This model has been around for a while now but it’s still going strong. It was the most powerful among the freshwater lights tested and the most expensive, too. The price, however is well justified, as you will get full control over the strong CREE LEDs installed in seven different colours. The light has built-in fans, but they are quiet enough.
A perfect choice even for very high-energy planted tanks.
Phillips Coral Care 2018
This light just became obsolete (there is a Gen 2 version available) and has a suitably industrial look to match its ‘ancient’ nature. The reason is that this beast is so powerful that large-scale cooling is required. Being old doesn’t mean weak: it still can deliver a strong punch, so I would never use it untamed. Always get the optional programmable controller, as it will fry your corals.
TMC Reef Pulsar LPS-6
This design looks like a beauty from the future. It’s thin and sleek yet very powerful. The elegant body contains LEDs emitting the perfect mixture of blue lights required by LPS corals living in deeper waters.
The comprehensive Bluetooth controls 6 channels and lets you select suitable geographical pre-sets. It also allows full customisation, so you can create, save and even share your own settings. The light output I measured is more than enough for LPS and soft corals even near to the edges, so it’s probable that you will never need use this lamp at full power.