This I have noticed has been a subject of wonder or unsurity. I personally have one unit on my largest of four tanks.
What is a UV Sterilizer?
It is a process using ultra violet (UV) light for capturing and shocking sterile unwanted free floating bacteria, parasitic organisms, algae and ick parasite. The light in the UV attack the living cells by altering the structure of the cell's nuclear material. The halts the organism causing it to fail to reproduce, eradicating your aquarium of all aforementioned nuisances and blooms.
UV sterilization is accomplished by running water in an out of a chamber that contains a UV sterilizer bulb which is housed in a (quartz) glass sleeve that is in the shape of a tube like bulb.
Setting the unit up:
The 3 types of UV sterilizer units are in-line tank (water flows in and out of unit and marked on the housing as such) , hang-on version and pond version. Most units are designed to be hung upwards. The in-line units mount underneath the tank (mine is next to sump) using an external pump or routed from return pump to tank.
The hang-on version hangs the unit on the back of an aquarium. This type is easiest to set-up, but it is highly visible outside the stand being to some- unsightly. This is why I chose the sump as my location.
It is important that the pump used has adequate flow rate to allow water to pass through the unit. It is also important that the pump has a flow rate within the safe flow range of the uv sterilizer. The acceptable flow rates are determined by wattage, gph (gallons per hour of flow needed to sterilize bacteria or clarify the water of algae and method of flow ( hanging or sideways mount) Obviously the faster water travels through unit, the less effective it will be. Too slow is not good as sediment will be allow to stick to quartz sleeve. A moderate/steady slow is favorable.
What can be expected when using a UV unit:
UV sterilizers do as they are called; they sterilize free floating algae which has to travel through the sterilizer to be sterilized. If the objects cant be sent through the UV unit, it will not get sterilized. Additionally, they will treat and eliminate protozoan parasites such as ich during the new born, free swimming life cycle and adult stage of the parasite. Just like algae, parasites have to pass through the unit to be affected by UV. If the inhabitants have the disease already, unit will have no effect as the fish cannot swim through the unit.
Things to keep in mind when using a UV unit?
UV lighting can affect some dissolved chemical compounds in the aquarium and as with caution when medication .... just as advised to turn off protein skimmers, it is generally recommended also to turn the UV unit off when applying medications and other treatments.
One other point is to consider using a timer which will turn the UV unit On in the morning and shut it off in the early evening ( you can share this schedule with your lights) as many free floating beneficial foods, and phytoplankton in the tank emerge when the tank becomes dark and can be killed by a UV sterilizer.
Maintaining the sterilizer unit:
UV bulbs should be replaced annually or sooner if lower wattage type. Just like your tank lights, UV Lamps will lose its intensity and effectiveness and become ineffective as the bulb ages. If your tank has lots of suspended matter, or Detrious, you may need to clean the quartz sleeve that surrounds the UV bulb monthly to bi-monthly as the light needs to penetrate the sleeve to come into contact with the water that passes through. Cleaning can be accomplished by using either alcohol or vinegar/water mix.
Are UV sterilizers safe?
UV sterilizer lights as with any bright lights can damage the human eye so avoid staring at the bulb. Always remove unit from the mounting location and unplug them when working on them.
The 3 types mentioned:
hang on type: