Metal halide has long been the industry standard for high intensity reef lighting.  It is a proven lighting solution that can support any lighting needs in a reef tank.   Although metal halide lighting has such a great reputation, it also does have some weaknesses.  High Output T-5 lighting is the new kid on the block, but it has proven to have a few significant advantages over metal halide.  This article will discuss the pros and cons of each of these reef tank lighting systems.

What Metal Halide Lighting Does Right

Metal halide lighting has an excellent PAR rating and will penetrate deep into the water column.  Because the light from metal halide bulbs originates from a single point, it casts shadows in the tank similar to the sun and produces the much sought after “shimmer effect”.  It has a long standing track record of being able to support all types of coral life.

What Metal Halide Lighting Does Wrong

Uneven light distribution – Metal halide reef lighting comes from a single round light bulb or a series of round light bulbs.  These bulbs represent a single source of light just like the sun.  Because of this light distribution can be a bit uneven with a metal halide system.  This is one of the weaknesses of metal halide – it almost always leaves a more intense light in a cone shape directly under the bulbs.  This leaves dark spots between the bulbs and can sometimes create a “cone of death” where the light is too intense for most corals.

It gets HOT – Metal halide is very intense and the amount of heat generated can be quite surprising.   In my opinion, this is one of the biggest problems with metal halide lighting.  It will not only make your fish room hot, but it will also raise the temperature in your reef tank significantly.  This often leads to the need for an aquarium chiller to control the heat in the reef tank.  Also, with the heat of metal halides, there is an increased risk of fire.

It is inefficient – with rising energy costs it is becoming keluaran hk  increasingly more important to increase energy efficiency.  For a 125 gallon reef tank, it requires at least 750w of metal halide lighting to produce enough lighting to keep SPS corals.

It lacks actinic – In a display tank you will want to add additional actinic lighting.  This used to be accomplished with a VHO setup, but is increasingly accomplished with a few T5HO bulbs.

Poor bulb life – Metal halide bulbs only last about 9 months of normal use.

What High Output T-5 Lighting Does Right

Even light distribution – Because T5 bulbs are long tubes, they spread the light evenly across the tank.  This gives a much more uniform light distribution.

It gets LESS hot – High output T5 does get hot, but nowhere near as hot as metal halide.  Once I switched from metal halide to T5 on my reef tank, my average temperature dropped 4 degrees Fahrenheit.

It is more efficient – High output T5 is one of the most efficient lighting types available for reef tanks.  Some of the new LED systems are much more efficient, but they have not been tested long enough to prove long-term viability and growth.   To grow SPS corals in a 125 gallon reef tank it only requires eight 54w bulbs.  This works out to 432 watts of energy, or a 39% energy savings.


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