Fish, Tanks and Ponds

Fish, Tanks and Ponds
A comprehensive guide to fish

Aquarium Lighting

Fundulopanchax gardneri
Fundulopanchax gardneri


There are many types of aquarium lighting all with different applications, choosing the right lighting for the right application can have a big effect on the success of the tank. In the past the lights were there simply to illuminate the tank so that the inhabitants could be easily seen. But with today's more specialist aquariums being quite common place there is a bewildering assortment of lighting types and strengths available in every local aquarium shop.

Types of Lighting.

Tungsten light bulb

This type of light is not suitable for aquarium use for a number of reasons.

  • It get to hot, and cause over heating problems when used in a close fitting aquarium hood.
  • The spectrum of light emitted will not show the fish off to their best.
  • Plants will not grow very well with it.
  • If it gets splashed it will instantly fail.

Fluorescent Tubes (T8)

These lights are suitable for illuminating tanks that don't need very bright lights and aren't too deep. In order to grow plants successfully with them then you should use 2 to 4 tubes that run the full length of the tank and with properly made parabolic reflectors. They can be used for marine fish but only for a fish only set up.

Power Compact Fluorescent

These "U" shaped bulbs are much brighter than regular fluorescent tubes and can be used on planted tanks as well as some shallow reef tanks with soft corals which require lower lighting levels. They are more expensive then fluorescent tubes but you can get more lighting in a smaller space.

T5 Tubes

These tubes are great as they have a smaller diameter than the older T8 tubes and they produce more lumens with the same rating. This allows more tubes to be placed within a canopy thus more light in a tank. These tubes are great for a heavily planted tank some types of marine reef tanks

VHO (Very High Output)

These bulbs look like regular fluorescent bulbs but are run on a high powered ballast. These are very bright bulbs and can be used on deeper tanks that require high lighting demands. These are bright enough to be used on most reef tanks, including tanks with SPS corals. The draw back is that they don't last as long as regular fluorescent tubes and are expensive to replace.

Sodium Vapour

The spectrum isn't ideal to show the fish off to their best but plants do grow quite well with this kind of light. Unfortunately quite a lot of heat is produced and some means of keeping the water temp down during summer must be employed. It has largely been replaced by metal halides.

Metal Halide

The brightest light available. Needs to be kept cool or the tank will over heat. This is usually accomplished by either using a cooler or by fans in the aquarium hood. They come with a wide choice of spectrums so they can be used in either heavily deep planted tanks or reef tanks. However they need to be replaced between 8-12 months and can become expensive.

LED lighting

LED's are the newest lighting technology available.  The technology has come a long way and the modern high power LED's produce a lot of light in a small package.  They don't produce as much heat as the Metal Halides which they are slowly replacing, however they do produce heat which needs to be dissipated in order to maintain the life expectancy of the LED.; As with any new technology, they are currently very expensive to install on a tank, however once they are purchased they can last in the order of ten years without the need for replacement.


Electrical timers are very cheap and accurate. They will take the guess work and keep the lighting on an even schedule which is important for all but the fish only aquarium. A timer can also be linked to other aquarium equipment such as a CO2 unit on a planted tank which ensures that the CO2 is only administered while the tank is illuminated. The use of a timer for aquarium lighting is highly recommended.

Lighting Terminology


Temperature ratingTemperature of a bulb is measured in degrees Kelvin. A common and understandable misperception is that the temperature of a bulb refers to heat that the bulb will create while it is running. In actuality, the temperature markings on lights refer to the colour that the bulbs put out. The higher the temperature rating the more bluish the light will be. A daylight bulb (same colour as noonday sun) will have a temperature rating of around 5500K to 6500K (depending on manufacturer)


LUXThis is the measurement of the lights intensity. The higher the lux, the more light the bulb puts out and the deeper it will penetrate into the water. This is important for deep tanks with either corals or plants. The lower the temperature bulb you have the more intense the light it will put out, therefore a 5500K daylight bulb will have more light output then a 10000K bulb of the same wattage.


Spectrum imageThe spectrum of a bulb shows how the overall visible light is distributed throughout the colour band. There are three main colour spikes to keep an eye out for: blue, green (indigo) and red. The red band is generally highly desired in freshwater-planted tanks. Green plants use light from the red spectrum the most to photosynthesis. If there is a high concentration of blue and green light in a planted tank, it's more likely that algae will be able thrive better than the plants. On the other hand, deep-sea animals such as corals and anemones utilize a lot of the blue spectrum.

Lighting application

Ordinary fish only aquarium:
The most commonly used lighting for a small or large community tank where plants don't really form part of the feature or where plastic plants are used are fluorescent tubes. These come in a variety of spectrums some which replicate daylight and others designed to enhance the colours of the fish. One or two tubes is normally sufficient for this and for a limited duration or algae may become a problem.

Use natural daylight through the daytime which is ample for the fish and put the lights on for just a few hours each evening. The lights should be positioned towards the front of the aquarium hood so that the light reflects back off the fish rather than creating a silhouette when the lights are positioned to far back in the hood.

Planted aquarium

Plants need light, it is with the action of light which allows plants to photosynthesize. Most planted aquariums aim to use between 2 to 5 watts of fluorescent lighting per gallon (based on US gallons and T8 or T12 tubes with reflectors). Illuminated for approximately 10 hours per day.

With the use of so much lighting and reflectors the lights will take up most of the hood and so can't be positioned to reflect light off the fish. But using tubes with different spectrums can help. If a colour enhancing tube is positioned to the front of the hood and the rest of the tubes which favour the plants are placed behind it in the hood then the fish will still be seen to their best advantage while keeping the plants happy too.

Reef aquarium

Reef aquariums include lots of organisms which are both animal and plant, or in more simple terms animals which have a symbiotic relationship with certain types of algae which lives in their tissue. Theses animals obtain most of their food from the sugars made by the algae and if the algae dies the animal may starve. These creature need exceptionally intense lighting in order to thrive, more than fluorescent tubes can provide.

The lighting of choice for these aquariums is provided by metal halide bulbs in the right spectrum. The big disadvantage with these bulbs is that they also produce a tremendous amount of heat which means that some form of cooling has to be incorporated into the aquarium hood, such as fans or a more expensive aquarium cooling device.

Recently there has been a move towards LED lighting which is still in its infancy but is improving all the time. Reef aquariums normally require 10 to 12 hours of lighting per day. Metal halide lighting is very expensive to both purchase and to run while LED lighting is expensive to purchase but much cheaper and longer lasting to run.