Marine Lighting

The type and amount of lighting is one of the most important considerations when setting up a new marine aquarium. There are types of lighting to suit most budgets, all with their own pros and cons for specific applications. If you are considering a ‘Fish only’ system the amount of lighting is less of a factor in the success of your aquarium than it would be if you wish to create a ‘Reef aquarium’. In this guide we will look at the various types of lighting available and the reasons for choosing (or not choosing) each one.  We will also look briefly at the intensity of light required by different types of saltwater aquariums.


Fish Only Systems

If you intend to keep fish only (i.e. no corals or other invertebrates) then the lighting does not need to be too intense, in fact, lighting which is too intense could lead to nuisance algae problems within a fish only aquarium. The lighting should still be of the correct spectrum for a marine aquarium in order to mimic the sunlight found in the inhabitants natural habitat. A combination of ‘Marine White’ and ‘Marine Blue’ (actinic) lighting is preferable in most cases.

Suggested lighting type: T5, T8, LED


Fish Only With Live Rock

The lighting required for this type of aquarium is the same as that of the Fish Only system outlined above. However, if you increase the lighting slightly the aquarium will benefit.

Suggested lighting type: T5, LED


Soft Coral Reef

As this aquarium will most likely contain photosynthetic invertebrates the lighting required will be more intense than the previous types of marine aquarium mentioned. Most (though not all) soft corals require light to grow and flourish. A 50:50 marine white/marine blue ratio is a good starting point and will be desirable to both your corals and yourself from an aesthetic point of view.

Suggested lighting type: T5, Metal Halide, LED


Full Reef Aquarium

The lighting required for a full reef aquarium (i.e. an aquarium containing SPS/LPS corals) is significantly more intense than for any other type of marine aquarium. Insufficient lighting can result in coral bleaching or coral death. Most corals have a symbiotic relationship with algae which lives inside the tissue of their body. The algae use light to photosynthesise and the coral feeds on the by-products of this procedure, insufficient lighting will therefore cause the coral to effectively starve to death over a period of time. As a general rule of thumb for a reef aquarium you should aim for 1 watt of lighting per litre of aquarium water. This should be used as a guideline only as many factors such as aquarium depth, tank inhabitants and surface area of the tank have an effect on the lighting required. We would advise that T5 lighting should not be used on aquariums deeper than 30” without additional metal halide lighting unless no corals are placed below this point.

Suggested lighting type: T5, Metal Halide, LED


Lighting types

So, you’ve decided on which type of aquarium you wish to set up, you know how intense the lighting should be and you know which types of lighting are able to provide this, but, wish type should you purchase? Now we will take a look at the pros and cons of each lighting type.



T8 lighting is probably the most common form of lighting supplied with ‘Complete’ aquariums. The tubes are 1 inch in diameter and are available in many different lengths and outputs. One of the main advantages of this type of lighting is that, as mentioned above, if you have purchased a ‘complete’ aquarium and wish to convert it to marine it is relatively straightforward to retro fit the lighting as a tube change is all that is required.

Fluorescent light tubes become less efficient after 9-12 months and the colour temperature can shift. This means that in order to keep your aquarium looking at its best you must replace the tubes every 9-12 months.

The output of this type of lighting is considered to be quite low in relation to other types of lighting available today which means that they are only really suited to a fish only system.

Fitting reflectors to T8 lighting is definitely something that we would recommend. Doing this can increase the light actually reaching the aquarium by up to 100%.

T8 lighting should only be used on aquariums up to 24” deep.



T5 lighting is becoming an increasingly common choice amongst aquarium manufacturers when selecting the lighting that is included with aquariums. This is good news for the same reason as T8 lighting. Retro fitting marine specific lighting involves merely changing the bulbs.

T5 lighting is similar in physical appearance to T8 lighting but is 5/8 inch in diameter. The T5 tube will produce a significantly higher output when compared to the same length of T8 lamp, e.g. a 48” T8 tube produces 36w of light whereas a 48” T5 tube will produce 54w. While T5 lighting is marginally more expensive than T8 lighting, in terms of ‘bang for buck’ the T5 represents better value.

As with T8 tubes, these lamps will need to be replaced every 9-12 months due to light quality degradation.

T5 tubes generate heat which can be an issue in aquariums with hoods, although the heat output is not normally an issue.

As with T8 tubes, reflectors can be fitted to T5 lamps to greatly increase their useful output.

Using T5 lighting in your aquarium normally allows you to easily upgrade once your experience (and wallet) allows. Adding more T5 tubes is an easy way to increase light output if you decide to move from soft corals to LPS/SPS. You will need an appropriate lighting controller and the bulbs to add more lighting. The controller is normally positioned in the cupboard out of sight, and the new lights attached to the existing hood using the brackets supplied with the controller.

T5 tubes should only be used on aquariums up to 30” deep unless they are being used as supplemental lighting to metal halides.


Metal Halide

Metal halide lighting was, until very recently, seen as the only real choice for lighting a full reef aquarium due to its high light output capabilities. Using metal halides also creates a pleasing (and natural looking) shimmer effect on the sand bed and corals in an aquarium.

Metal halides are capable of penetrating the aquarium water to greater depths than other forms of lighting, although LED technology is rapidly improving in this area. As a general rule we would suggest using the following as a minimum for a full reef aquarium:

18” Depth = 150w Metal Halide

24” Depth = 250w Metal Halide

24+” Depth = 400w Metal Halide

Metal halides will need to be suspended above the aquarium either from a wall or a ceiling. This gives the benefit of being able to easily adjust the distance between the light source and the water surface to fine tune spread of light and intensity.

As metal halides generate a significant amount of heat, suspending them above the tank allows for air flow around the units and the surface of the water to aid cooling. In summer, fans may be required to keep things cool.

Bulbs in metal halide units will need to be replaced every 8-12 months.

Metal halides normally need to be supplemented with actinic T5 lights to provide the correct light spectrum for coral growth.

The running costs and energy consumption of metal halide lighting are considerable. However, if you wish to keep SPS corals successfully in a relatively deep aquarium, they are almost a necessity. LED lighting is now capable of giving comparable performance.

If using more than 1 metal halide lamp to light your aquarium you may find that a chiller becomes essential in order to keep the aquariums temperatures in check.



LED lighting is still considered to be the ‘new boy’ amongst aquarium lighting choices but it is quickly proving itself to be an extremely viable and cost effective solution.

The latest generation of LED lighting, such as the TMC AquaRay range, boast impressive light output figures and low running costs.

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.

LED’s use very little energy, and the energy they do use is converted into light very efficiently, which reduces the heat output of your lighting system removing the need for expensive cooling equipment.

The coverage of LED lighting is quite concentrated and so for larger aquariums, quite a few units will be required to get an even spread of light. As with metal halide, LED lighting is a point light source and so, creates a shimmer effect.

LED lighting is controllable (depending on brand) allowing for dawn/dusk effects amongst other things. This creates a more natural environment for your tank inhabitants and reduces stress for your fish.


Running cost comparison

This table shows the running costs (for lighting) for a 36x18x18 aquarium containing a mix of SPS and soft corals. Costs are based on the lights being on for 10 hours per day.


Equipment Running 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

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