UV sterilization has been utilized for many years with great benefits for society. It is widely used in the medical industries and water purification industries. The sterilization process is done by the radiation given off of the UV bulb. The radiation coming from the light would scramble the DNA of virtually any organisms thus, it is neutralized. UV is widely used for water purification as it sterilizes water that passes trough – neutralizing bacterias, viruses, fungus and parasites.
The benefits of running a UV filter on your aquarium would be to keep any algae, virus, bacteria, fungus and parasites at bay. This is not to say that if your aquarium is currently having some type of outbreak that a UV filter would fix it. The UV would only sterilize anything it comes in contact with. That means for a UV filter, only water passing trough the UV would become sterilized. For example if you currently have an Ich parasite outbreak. Any Ich that passes trough the filter will be neutralized but any Ich currently on your fish will be fine.
Having a UV filter will also help control free floating algae and keep bacteria blooms from occurring in your aquarium. You will notice better water clarity within days. Cloudy water tends to be caused by an over abundance of bacteria. Normally the cause is from having too much nutrients in the water (over feeding). It can also be caused by having algae free floating in the water. This is consider green water. Green water is caused also by having too much nutrient in the water. Thus providing a perfect environment for algae and bacteria to bloom.
Each UV utilizes a different design. Some better than others but all have the same function. Typical UV designs are to be used in-line with a canister filter/pump or with recent advances in the hobby UV filters are now available in a Hang on back design similar to hang on back filters but with the added benefit of UV sterilization.
UV filters tend to prolong water contact time with the lamp inside the reaction chamber. Typically the UV bulb itself is housed in a Quartz glass sleeve. (Quartz glass is used as to not degrade the concentration of UV being generated by the bulb.) The prolong contact time is done by using channels which rides along side the quartz sleeve.
There are pretty much no drawbacks to using a UV filter in an aquarium. Please make sure to use good quality UV filters from reputable company. UV filters are rated by wattage to tank size. The ideal rating is roughly 1 watt of UV per 3 gallons of water.
(The UV radiation coming from the bulb is extremely dangerous to the skin, eyes, or any part of your body it contacts. UV filters are specifically design to run safe and securely on your aquarium. Please follow manufacturers instructions. Refer to owners manual for any concerns.)