Review: Arcadia OT2 LED – Hybrid T5/LED Light Unit

Following on from experiments in which we sought to enhance SPS coral colouration in our test system with a programme of trace element supplementation, we decided to upgrade the lighting on our test tank and finally took the plunge into the realm of LED lighting.

After using Metal Halides for a number of years, we were pretty sceptical about the ability of LEDs to provide sufficient usable light for coral growth (let alone good colour) despite the marketing hype. Also, the whole LED market seemed confusing initially and there are obviously some substandard units on the market. For this reason, we decided to stick with a well-regarded UK manufacturer and went for an Arcadia OT2 LED Hybrid T5 and LED system.

Although it perhaps doesn’t offer some of the expanded LED colour combinations of the latest units, this unit it clearly constructed to the highest standards and looks absolutely beautiful…. sleek and silver. It also offers one of the highest levels of controllability we could find, with 4 channels (two T5 and two LED) each dimmable in 1% increments over minutes or hours. Of course the inclusion of all those T5s is something that many other units don’t offer and in our view this compliments the 450nm blue/8k white LED array providing for a wide range of colour combinations. It also provides for the best of both worlds… shimmer effect from the panels of 3watt Cree LEDs and a uniform, colour-enhancing glow from the tubes.

It’s worth remembering that this is quite a wide unit… around 18″ front to back, so its best suited to tanks of that size or greater. Although legs are available to stand it on your tank, we chose to hang it from our existing Arcadia wall brackets and it was really easy to install. Once in position, removable flaps allow for access to the T5 banks from above, so you won’t have to move it out of position to change them… a great design feature in our opinion. We estimate the unit weighs a similar amount to our old halide unit, around 6kg.

Once in position, it was necessary to ‘burn in’ the new T5s for 100 hours before they could be dimmed. Luckily the controller provides a function to help you keep track of this. When it came time to set our dimming programme, the controller was exceptionally easy to use. It was even possible to set a realistic moonlight programme based on actual moon cycles. The effect of the dimming is truly stunning.

OK, so fancy design and control aside, can this unit actually provide usable light for a reef? Well, after running this unit for 3 months we have no hesitation in confirming that it can keep even the most light hungry organisms happy. PAR level tests (using an Apogee Quantum sensor) show levels are greatest under the LED array which provides a fairly narrow strip of very high intensity light (specifically, with the unit suspended 6 inches above the water surface, PAR levels ranged from over 500 just under the water surface to around 300 at a water depth of 16″). This makes it particularly suited to tanks with a central ridge of rockwork and we found it even kept a Tridcana maxima clam healthy around 12″ under the water surface. Although we can’t definitively say that this light was solely responsible, we did also notice enhanced SPS colouration after running this unit for a few weeks.

In terms of pricing, this unit certainly isn’t the cheapest (prices start at around £) but remember it does combine a both high quality T5 and LED arrays into one stunning modern unit, and offers a superb level of control.

For more details, take a look at the spec sheet HERE

Don’t forget to catch UltraMarine magazine issue 34 for our feature ‘Reef Restorations: Revisited’ which takes a wider look at developments in our test system over the last few months, along with additional images.

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