A guide to freshwater lighting


Lighting is one of the major considerations when setting up a successful freshwater aquarium. You will need to consider the intensity of lighting, the duration of the lighting each day and the spectrum of the lights. The light spectrum is just as important, if not more important than the wattage of the lamps.

The type of light required for a coldwater aquarium is normally down to the tastes of the owner more than the requirements of the fish. The best lighting for a coldwater aquarium will show off the colouring of the inhabitants to make them look their best. Although the lighting itself is not hugely important, it should still fall within the correct area of the light spectrum, especially if there are plants within the aquarium. If there are plants present the lamps should be within 5500-6500 Kelvin and reasonably high output, such as T5’s.

T8 lighting is sufficient for most coldwater aqauriums. This means that many ‘Complete’ aquariums on the market today are suitable for keeping coldwater fish without any lighting modifications.

As with coldwater aquariums, the lighting required for a tropical aquarium should show off the colours of your fish. There are several different types of light tube which can be used, all output a slightly different area of the light spectrum. ‘Daylight’ lamps use more of the blue end of the spectrum to recreate, not surprisingly, daylight! Whereas ‘warm’ light tubes utilise the red end of the spectrum to show off the colours on your fish.

If possible, using a combination of these lights gives a good coverage and a pleasing look for your aquarium.

If you wish to set up a planted aquarium, more care will need to be taken when selecting lights in order to ensure that your plants flourish. There are several T5 bulbs on the market designed specifically for planted aquariums such as Arcadia’s Plant Pro range.

In a planted aquarium you should aim for 1 watt of light for every 2 litres of water as a minimum. Obviously there are plants available which will be ok under less intense lighting but 1 watt per 2 litres is a good ratio to aim for when starting out. It is also a good idea to install reflectors on your light tubes to maximise the amount of light reaching the aquarium.

LED lighting is now available aimed specifically at the planted aquarium hobbyist from companies such as TMC who offer the Grobeam range. These offer a full spectrum light output of 6500K and, as it is a point light source they create a natural shimmer effect.

Light tubes should be changed every 8-12 months as the light output diminishes and the spectrum of the light can shift slightly leading to algae issues. This does not apply to LED lighting as bulbs never need to be changed.

A light timer is an essential piece of equipment for any aquarium and allows for consistency in the day to day cycle of light within the aquarium. Aim for 8-10 hours of ‘daylight’ per day. If the tank receives a large amount of direct natural light (something you should aim to avoid when positioning your aquarium) then consider reducing this lighting period, especially if algae problems occur.

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