Cloudy water, algae blooms that are never-ending, or persistent diseases that are plaguing your aquarium may be able to be solved with the addition of a UV (Ultraviolet - a spectrum of light) Sterilizer. Although this shouldn't be considered the first step of action when it comes to solving one of these issues, it can allow you to identify the other root causes (if there are any that can be fixed) while you can focus more on the aquarium as a whole. Even the best-taken care of aquariums can have excess algae growth that may not be specifically related to the lighting fixture but could be related to inhabitant activity, the types of foods that are being used, or even lighting in the room from other fixtures of windows shining into the aquarium.
Algae is normally seen as either the start of getting an aquarium setup (due to all of the excess nutrients) or seen as an aspect that shows that the chemistry is perfectly balanced out (since specific types of algae require good nutrients within the water and the specific levels of lighting). Additionally, UV sterilizers can be used to kill any harmful bacteria that may be present inside of the aquarium. A vast majority of parasitic and bacterial infections can be killed if UV sterilizers were being used, however many do not know that these given organisms live within their aquarium. Medicines can only be effective once it is known what is affecting the inhabitants, and is normally only able to be given once the given parasitic or bacterial infection has infected the fish to a degree where it is visible to the human eye. However, it is to be noted that ultraviolet light can only target free-floating microorganisms, and will not be harmful to those that are attached (or inside) or fish, on substrates, plants, decorations, corals, or the walls of the aquarium.
With any piece of aquarium equipment, there are various types of UV sterilizers that all have their advantages and negatives. Some units can be sold as standalone units, some are built into filters, others can be added into the existing piping of filters, but almost all of them have a rated lifetime for the light before it needs to be replaced (even if it appears to not be burnt out). To be most effective, there should be a flow rate that is controlled to allow for the UV sterilizer to process the water moving past it fully per the given manufacturer's specifications. For most, adding the UV sterilizer at the end of a filter is more effective as the ultraviolet light is not blocked by any debris that may be sucked in at the beginning of the filtration process. It is to be noted, however, that after around 6 month the light may still be turning on/running, however the effectiveness of the ultraviolet rays it produces will decrease drastically unless there aren't any ultraviolet rays being generated and instead just some visible light.
Incorporating an Aquarium UV Sterilizer can allow you to not only get rid of any excess algae but has a range of more benefits that are many do not consider. You can boost the effectiveness of your filtration, clarity of the water by preventing any free-floating algae from being able to settle down, and lastly, put additional safeguards towards the health to your aquarium by preventing microorganisms from spreading rapidly. In many cases, the benefit is great if the aquarium is in a location that will always have algae, contains a vast majority of rare or priced inhabitants or in situations such as a outdoor pond where filtration can only go so far in order to prevent algae buildup in the water itself or on the rocks.