Ultraviolet Sterilizers - Purpose, Advantages and Disadvantages

What is an Ultraviolet Sterilizer and how does it work?

Ultraviolet sterilizers have been around for many years but were mostly used for outdoors ponds, nowadays they are becoming more popular with aquarium keepers and can serve a useful purpose for them. They work basically by pumping the water over a tube that produces Ultraviolet rays, this will remove from the water any unwanted microscopic bacteria, parasites,fungal cells and even pathogens. It will also prevent a lot of algal growth in the tank as the rays will destroy a high percentage of algal spores that are present in the water. The Ultraviolet rays actually penetrate the living cells of these microscopic creatures and destroys their DNA making them lifeless and they quickly die off. There is a mixed consensus of opinion as to whether these are a worthwhile investment in the aquarium, some keepers swear by them while others shy away from them and prefer to control the water quality by other means.

The most common Ultraviolet Sterilizer available to purchase nowadays is the Quartz sleeved type but they are also available in the tray type, these are where the UV bulbs are suspended above a tray of slow moving water and the casing that the bulbs are enclosed in is usually made from a reflective material to bounce all of the rays into the water flow.

There is also the Wet tube type where the tube is enclosed in a waterproof tube and the water will pass directly in front of the tube. The Quartz type houses the tube in a Quartz sleeve which protects the tube from contact with the water and these are usually the most effective as the tubes can be cleaned on a regular basis without too much trouble.

How do I know which Ultraviolet Sterilizer I need for my aquarium?

Ultraviolet Sterilizers are normally rated on the wattage of the tube, smaller tanks up to 40 gallons will require up to a 10 watts unit, larger tanks up to 100 gallons will need a 20-25 watt unit and any tanks larger than this can go up to units that run on 40 watts. It is very important to use the Ultraviolet unit that is rated for your tank size, if it is not large enough it will not be effective and if it is too large it may sterilize your water too much making it too pure for the fish. It is also important that the water flow passes through the unit at the correct speed so that it can control the impurities efficiently, as most units are linked to the filters of the aquarium it may mean slowing the filters down slightly to get the correct water flow. One important point to remember when fixing one of these units to the tank is always place after the filter, if the unit is placed before the filter it can destroy some of the beneficial bacteria that the filter depends on.

Ultraviolet Sterilizers, picture 1

Key points on running an Ultraviolet Sterilizer:-

Always check out the shelf life of the tube that you are adding to the UV unit. Some units require the tube to be changed every 6 months, other units require the tube to be replaced every 12 months , always follow the recommended guidelines.
Never remove the tube sleeve from the unit while it is switched on, the rays can be harmful to your eyes and also cause skin irritations.
Ultraviolet Sterilizers need to be run on a 24/7 basis to be fully efficient.
Always use a unit that is rated for the water volume that it is treating.
Never use the unit before the filtration system, always connect it after the filter.

Advantages of using an Ultraviolet Sterilizer:-

When used in outside ponds they make a very effective deterrent for algal growth, this is not quite so apparent in the aquarium.
There are no pathogens that are resistant to the rays that the units transmit so they will eradicate any diseases or viruses which could affect your fishes health.
Nowadays most units are quite cheap to purchase, units designed for ponds will be more expensive as they are rated at a higher power and require larger components.

Disadvantages of using an Ultraviolet Sterilizer:-

Ultraviolet Sterilizers require electricity to work, the running costs will increase according to the amount of wattage the unit requires.
It is a common belief that using these units will weaken the fishes immune system, the fish do not build up a resistance to disease or bacteria if they do not come into contact with them.
When adding any medication to the tank or pond the units need to be turned off or they will weaken the efficiency of the medication added.
Some of the older units are bulky and can take up a lot of space in the cabinets or if they are internal Ultraviolet Sterilizers they are visible in the aquarium and will take up space.
The units will need regular maintenance i.e. the tubes must be kept clear from any form of debris or sediment for the rays to penetrate the water as it passes through.

Ultraviolet Sterilizers have changed a lot over the years, when they were first available to purchase for pond keepers and aquarium keepers they were separate units and very bulky, nowadays they are much more slimline and also much more efficient. Many of the leading filter manufacturers will often have them built into the filtration systems so that they are out of sight and work as soon as the filter is switched on. This innovation was first used in pond filtration and proved to be very popular, Hozelock provide various sized filtration units for different water volumes. Eheim have brought out a range of aquarium filters with built in Ultraviolet Sterilizers, this has proven to be of a great benefit to keepers with restricted space in their cabinets and keeps all of the equipment tidy and neat.

I hope that reading through this article helps you to understand how these units work and help you to make up your mind as to whether it is worth you investing in one for your aquarium or pond.