Why should I use a metal halide lamp?
Metal halide is commonly accepted as the best substitute for nature when it comes to aquarium lighting.

The exceptionally high light output when compared to other lamp types such as fluorescent tubes, makes them a very effective light source, particularly for the larger tank set-up.

Commonly used in marine aquariums, they can also be a very useful asset in freshwater tanks - particular those where good plant growth is desired.

Metal halide lamps for marine aquariums
When choosing a lamp for use over a marine aquarium, there are two factors that are important.

Firstly, the light output has to be beneficial to the health of the livestock. This is particularly important in tanks containing invertebrates such as corals (hard or soft), anemones, and Tridacna clams.

A suitable light is one which promotes photosynthesis by the microscopic algae (zooxanthellae) which live within the tissues of such invertebrates.

This relationship between the algae and its host animal is extremely important. If the algae do not flourish within the tissue, then the health of the host animal will suffer, and in many cases will ultimately lead to death if not corrected.

Combined with this, a lamp must provide an effect which is visually pleasing to the eye of the fish keeper.

We all want the creatures in our care to be as healthy as possible, but if we can achieve this without compromising the aesthetic appeal, so much the better.

This is why we have developed our new 14,000 Kelvin lamp.

The output actively promotes photosynthesis within the tissues of those invertebrates which utilise symbiotic zooxanthellae, and so allowing healthy growth.

Visually, the appearance is very clear and crisp, with excellent colour rendition, resulting in a very natural looking picture within the confines of the aquarium.

The lamp is available in three sizes - 150W, 250W, and 400W - The latter being particularly for the deeper than average aquarium, or those containing species of stony corals with a very high light demand.

NEW '20,000K' metal halide lamp
As light passes through seawater, much of the visual content is filtered out rapidly - with the light at the red end of the spectrum being the light that penetrates least, and the blue end penetrating the furthest.

As a result the light on reefs in the natural environment changes rapidly as the water depth increases. At the very surface, down to a depth of only a few feet, the light in the water has a bright blue-white appearance, as replicated by the 14,000K lamp.

As depth increases, and the light is gradually lost - starting at the red end of the spectrum, the water takes on a deeper blue appearance. Photosynthetic invertebrates at this depth have evolved to rely purely on this blue light, and have lost the ability to photosynthesise using red light (as land plants do).

The '20,000K' lamp has been developed to replicate this environment in the slightly deeper water - providing the light levels that the organisms need, and also creating an attractive 'moonlight' effect in the aquarium.

The Arcadia Series 3 range of pendants is an ideal way of housing, and optimising metal halide lamps.

They contain a specifically designed reflector, which focuses the lamps output into the aquarium, and by using the adjustable deflectors, the light spread can be altered to cover the entire aquarium without causing glare to any onlookers.

With the exception of the mini version, all models contain supplementary lighting from fluorescent tubes, and built in timers, so that a fixed daily photoperiod can be set.

Which lamp to choose
The following table gives brief details of the Arcadia Metal halide lamp range

How do I maximise the benefits of the lamps themselves?