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The subject of reef tank lighting is one of the most controversial subjects in the hobby. It is often such a hotly debated topic as people have had varying degrees of success or failure with each different type of lighting. The most important criteria to keep in mind when choosing your lighting is what type is best suited for your setup and the inhabitants you wish to keep. While appearance of the tank is certainly a consideration the health and wellbeing of your fish and corals should be the priority. The intensity and spectrum of the light are vital for the symbiotic zooxanthellae relationship that many corals rely upon. The height and overall size of the tank will play an important determining factor in which lighting option is best.


The three main types of fluorescent aquarium lighting are Normal Output (NO), High Output (HO), and Very High Output (VHO). All of these fluorescents are linear in form, thus distributing light evenly across the water surface.  The advantage of fluorescents is that they produce less heat than Metal Halides but will generally need to be replaced every six months and can be rather expensive when using a multi-tube housing.

  • NO: The availability and cost of NO lights are the main advantage while the main disadvantage is that they produce the least intensity of the fluorescent bulbs. They are best suited for small, low light, reef tanks housing such corals as mushrooms, certain soft corals and some LPS. You may find however that the rate of growth with NO bulbs is significantly slower. 
  • HO: When purchasing T5’s ensure that you are getting High Output T5’s (T5H). All T5 bulbs must be run on an electronic ballast. T5's have a higher lumen output than a VHO, generate less heat, and are more energy efficient. At only 5/8" in diameter, more bulbs can fit under your tank's canopy. 
  • VHO: Requiring a special ballast, cable of handling their power, these bulbs put out almost three times more light than NO bulbs. The light output also tends to have a more even spread. However the side effect of this is greater heat output. A greater selection of corals can be kept under VHO lighting including some SPS if kept towards the top. It is suggested to be used on tanks that are maximum of 24” tall. 
  • Compact Fluorescents: The technology is similar to VHO but is only powered on one end and “U” shaped which allows more wattage in a smaller size. One disadvantage is that there are not as many color temperatures available as VHO tubes. 


There are two options when it comes to ballasts for fluorescent lights: core coil ballasts and electronic ballasts. The most typical, core and coil ballasts are heavier, produce more heat and use more electricity. Electronic ballasts cost more but produce less heat and use less heat. They are also lighter which makes placement more versatile.

Fluorescent Tube Color Options:

  • Full spectrum: Most popular is the daylight (6500K) which is recommended for SPS and clams. 
  • 50/50: Combination of actinic and daylight it is equivalent to 10,000K and is recommended for soft corals and LPS.
  • Actinic: Often used in combination with other tubes to enhance, or pop, the colors of the corals.

There are many benefits to installing LED aquarium lighting in your tank and only a few disadvantages. First of all, LED bulbs and LED lighting systems are energy saving in comparison to traditional tank lighting methods.  LED bulbs can last for several years .  This saves money in bulb replacement costs.  LED lights put off less heat inside your aquarium as well.  A big disadvantage for some might be the initial cost to switch an existing tanks lighting over to LED lighting. LED lighting is more expensive than traditional tank lighting. Another benefit of LEDs is the fact that they can easily be dimmed and controlled. Controlling LEDs can actually be quite simple, but also allows for some more complex setups and effects that you simply can't do with any other lighting source.

Currently, the top end high power LEDs are right behind metal halide and T5 in terms of efficiency, so you can produce almost as much light (lumens) for the same wattage. But producing light, lumens in this case, is not what LEDs are all about. The real clincher is the ability to produce more PAR (Photosynthetic Active Radiation) per watt than most any other form of light. For those that don't know, PAR is a measurement of the amount of light that falls onto an area, that falls on a response curve for photosynthesis (400-700nm, ignoring UV and IR light). Basically what this means is that more PAR equals more growth out of photosynthetic corals. Because of this, LEDs do not have to produce as many lumens as other forms of light to reach the same growth potential.

Metal Halide lighting is a type of lighting known as High Intensity Discharge (HID) lighting. Metal halide lamps are available in a wide variety of wattages and color temperatures.  The higher the color temperature of a bulb (in degrees Kelvin), the bluer the light will be.  The main advantage of metal halide lighting is they are very bright and best simulate natural sunlight. However the light produced is more directional and not as evenly diffused. Metal halides may not be the best option where soft corals are the predominant corals and run the risk of bleaching SPS if the corals are not gradually acclimated to them.  They also run very hot being dangerous to the touch and transferring heat to the water and the surrounding room. Therefore the use of fans or a chiller to maintain optimal water temperatures may be required.  Metal halide bulbs should be replaced every 9-10 months (~3,000 hours of use).

Some power recommendations:

  • One bulb for every two-foot square area of tank surface
  • Tanks <20” one 175w mh bulb per two square feet of tank surface area
  • Tanks 20”-30” one 250w per two square feet of tank surface area
  • Tanks >30” one 400w per two square feet of tank surface area 

* These are just recommendations, not guidelines, as depending on the inhabitants kept your lighting requirements will vary. Also placement of corals in a tank with metal halide lighting will be an important consideration.

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