Understanding Marine Aquarium Lighting 2

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When you look at a marine aquarium, you will see beautiful bright colored fish, rocks, reef aquaria and other underwater inhabitants showcased in a clean and well-lit glass or acrylic tank. A balanced, safe and viable marine aquarium requires stringent water quality monitoring and distinct marine aquarium lighting.

If you are planning on setting up a marine aquarium, it’s imperative to know the differences between aquarium light sources and choose the one that will work best for your budget, your tank and your aquarium inhabitants.

Before you choose your marine aquarium lighting, there are many factors to be aware of and questions to ask yourself and most importantly, what type of aquarium are you planning to have;

  • a fish only with live rock,
  • soft coral reef,
  • full reef
  • or a fish only system?

Once you know what type of inhabitants will be living in your aquarium and you know the surface area and the depth of the tank, you can now move on to choosing the perfect lighting solution for your marine aquarium.


There are many different color spectrums of lighting to choose from; red, orange and yellow light will only penetrate a short distance in the water, while blue and white light will penetrate the deepest.

Here is some more information about light spectrum through water:-

“Light spectrum is measured by the Kelvin scale. Natural sunlight on a clear day registers at 5500-Kelvin degrees.

Kelvin temperatures less than 5500 become more red and yellow and the higher the Kelvin temperature the bluer the light is.

Photosynthetic invertebrates should be kept under lamps rated at or near the Kelvin temperature where the invertebrate was collected.

Shallow water species should be kept under 10000K lamps while deep-water species would prefer 20000K lighting.”(source)

Choosing Your Lighting

Natural Sunlight

Your aquarium should be placed away from direct sunlight and places where there are fluctuating temperatures. Natural sunlight as a means for aquarium light is undesirable due to its yellow tint, low spectrum of lighting, and problems with unwanted algae.

Metal Halide

One of the most popular and natural looking lighting sources for most marine aquariums would be the metal halide lamp. These lamps are able to penetrate the water at deeper levels compared to fluorescent and LED lighting.

Because this light source can be hung from a ceiling or wall above the aquarium, a benefit to metal halides is that they can be easily adjusted. If you ever needed to change the distance from your light source to the water surface, it would be a simple task.

250-watt bulbs will work best in most aquariums unless the aquarium is deeper than 24’ and in that case, 400-watt bulbs would provide better light penetration. For every 2-3 feet of tank, it is recommended to have one halide bulb.

understanding marine aquarium lighting

Fluorescent Lighting

If you are looking for another type of lighting, high intensity fluorescents may be considered. Fluorescents display a more intense light and they are best used in soft coral reefs and full reef aquariums.

It’s essential to know what lighting requirements your tank inhabitants require. Without sufficient lighting, corals may not survive.

There are several different kinds of florescent lighting; two of the most popular kinds are T5 and T8 bulbs. These types of bulbs may be found in similar color ratings as the metal halide bulbs we previously mentioned.

T5 and T8 Lighting

T5 and T8 lighting come in the form of fluorescent tubes that are 5/8th inch to 1 inch in diameter and come in many different outputs and lengths. In order to help explain the differences and similarities of both bulbs, here is a helpful list:


  • Easy to change tubes
  • 5/8th inch diameter
  • Higher light output than T8
  • More expensive than LED and T8 lighting but better value in the long run
  • Short lifespan, bulbs should be changed every 9-12 months
  • Easier to upgrade and add more lighting if necessary
  • Most efficient for aquariums up to 30” deep.
  • May be used as supplemental lighting to metal halides


  • Easy to change tubes
  • 1 inch in diameter
  • When using reflectors, light will reach the entire aquarium
  • Short lifespan, bulbs should be changed every 9-12 months
  • Low output compared to LED and metal halide lighting
  • Most effective in aquariums up to 24”deep
  • Need reflectors to get a full spread of light
  • Low light output
  • Best suited for fish only systems

LED Lights

LED lighting is still fairly new but has been proven to be cost effective and it’s used as a dependable lighting source.

If you do not wish to continually change your broken bulbs or maintain fluorescent lights periodically, perhaps LED lighting is your best option. Aquarium LED lights have a much longer lifespan than metal halide bulbs or fluorescent tubes.

LED Aquarium Lighting

Stunning Marine Reef LED Aquarium Lighting (pix source: Ecoxotic)

Because LED lights use a small amount of energy, they are a very efficient source and will require less cooling equipment to counteract any heat that they produce.

If you choose to go with LED lighting, you may need to use a few source points to make sure the light spreads evenly and provides proper concentration for the entire tank.

“Unlike fluorescent lighting and metal halide lighting, LED lights have a life of around 50,000 hours (that’s about 14 years at 10 hours a day!!!) with no noteworthy light quality degradation and less than 20% output reduction over that lifespan.

Taking into account how many times you would have to change fluorescent tubes or metal halide bulbs over that period, LED lighting is fantastic value for money.” (source)

Actinic Lighting

Actinic lighting is light that helps to facilitate photosynthesis, which is beneficial to coral and light sensitive invertebrate inhabitants.

This type of lighting is best used in reef aquariums. Actinic lighting is also very pleasing to the eye as it accentuates the fluorescents of fluorescent fish.

Suggested Lighting Types

Full Reef Aquarium: T5, Metal Halide, LED, Actinic lights

Soft Coral Reef: T5, Metal Halide, LED

Fish Only With Live Rock: T5, LED

Fish Only Systems: T5, T8, LED


High intensity lighting might lead to a considerable amount of heat to your aquarium, making it harder to keep the tank at its cool temperature.

Make sure you are keeping your marine aquarium temperature stable, as fluctuations between hot and cold can be detrimental to your marine environment.


Since you might be leaving your lights on for up to 10 hours per day, cost might be a factor when it comes to choosing the perfect marine aquarium lighting source.

The running costs for aquarium lighting will vary. LED lights will be the most economical while the T5 equipment will almost be triple the cost of LED lights.

Here is great running cost comparison done by Warehouse Aquatics. It’s in British Pounds (£) but is still gives an idea to what the costs are.

EquipmentRunning costs per month (based on 12p/kwh)
6 x 39w T5£8.54
1 x 150w metal halide & 2 x 39w actinic T5£8.32
2 x TMC Aquabeam 1500XG & 2 x TMC Aquabeam 600 Marine Blue LED’s£3.36

The running costs above are based on a 36x18x18 aquarium with lights on for 10 hours/day.


Here is a very helpful and detailed lighting overview chart created by drsfostersmith.com

Understanding Marine Aquarium Lighting Chart

Marine Aquarium Lighting Chart by Drs Fosters and Smith

Having a lighting routine cycle that mimics day and night is beneficial for fish and other inhabitants since it helps to establish a routine, makes them feel secure and allows them to rest.

As you can see, each type of lighting source has their advantages and disadvantages. As a general rule, lighting should mimic the sunlight found in the natural habitat of the inhabitants.

Share Your Thoughts

Hope the article above proves to be helpful for those of you trying to figure out the best marine aquarium lighting for your own aquarium setup. If you have any questions, please feel free to ask in the comments section below.

As always, don’t forget to share it with your friends by clicking the share button on the social media platform of your choice.

About Dennis Hanson

Dennis is an experienced aquarist with many years of knowledge and experience in keeping successful tanks. He also has no relations to the pop group Hanson.

2 thoughts on “Understanding Marine Aquarium Lighting

  1. Reply Mark Jun 13,2016 5:56 am

    I use natural sunlight for my reef tank (with chiller) and I have far better results than any other form of lighting. My corals are growing like nuts and its free. I don’t know how you can say it is “undesirable”. Natural sunlight is what these corals have evolved under over millions of years. If temps are controlled, it is by far the best for coral growth. There is no unwanted algae as long as all water parameters are good. I clean the glass of the tank every couple days as I would any other tank. No unwanted hair, bubble, or macroalgae. Did I say that it was free!

  2. Reply Fiona Currie Sep 20,2016 1:10 pm

    Good Day

    I need to replace the following with Led LIGHTING. Please advise?

    2x150w Metal Halide – LED Must be able to shine 1.3m down into water
    4x250w Metal Halide – LED Must be able to shine 1.3m down into water
    12 x 54w T5 Tubes – Fittings + LED Tubes Same spec as above

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