What is a UV Sterilizer?
A UV Sterilizer is a germicidal filtration device that uses UV-C Sterilization to filter the water resulting in clarification, lower disease pathogens, and removal of oxidizers in the water column resulting in improved Redox in your aquarium or pond.

 

How does a UV Sterilizer work?
A pump pushes the water through the UV Sterilizer at a specific flow rate, where the water will come in contact with the UV-C producing light either directly or indirectly via a quartz sleeve.

 

The UV Light then sterilizes the water by altering the DNA of organic matter as well as “clumping algae” in the water, and it is returned to your tank or pond.
How should I determine what my flow rate should be?
Your flow rate is dependent on the level of sterilization you desire from your tank. The slower the water moves across a UV bulb that is intended primarily for UVC production; the more time UV-C is in contact with the water. The slower the rate, the more sterilization you can achieve.
This goes hand in hand with a turnover rate.

What is a turnover rate?
Your turnover rate is the rate at which all your aquarium water is filtered in an hour. For UV Sterilization, you want a turnover rate of at least 1 1/2 times per hour. So if you have a 10 gallon tank, you want a turnover rate of at least 15 GPH. This will achieve level 1 sterilization when combined with the correct flow rate assuming other criteria are met as well.
What are the levels of UV Sterilization?
There is #Clarification, #Level 1, and #Level 2
Clarification is about 40-65 gph per watt with a good to excellent UV Sterilizer using a HO low pressure UV lamp.
This achieves Green water control in both Aquarium and Pond. This is the most popular application for ponds.
Level 1 Sterilization is about 20-35 gph per watt with good to excellent UV Sterilizer using a HO low pressure UV lamp [many poorly designed Chinese UVs with low output UVC lamps would bee to be slowed to a 10 gph or just to achieve level one sterilization].
This helps with Bacteria and some Virus’s. Level One is the most common & recommended aquarium application.
Level 2 Sterilization is about 8-12 gph per watt good to excellent UV Sterilizer using a HO low pressure UV lamp [not at all possible with most commonly sold discount UVs coming out of China & sold via Amazon & eBay].
This helps with Parasites and “Stubborn” Viruses. This is recommended for Swimming Pools (albeit generally impractical) and similar applications.
These flow rates for each level are also impacted by water turnover, UV-C Penetration, among other factors.