Choosing Your UV Sterilizer Size

Most of us have heard about the advantages of a UV sterilizer for the health of your body of water — be it an aquarium, pond, or even commercial zone. While size is a decisive factor for any UV sterilizer, there are variables at work here, such as flow rate, the type and size of the water body, and more to consider.

If you’re wondering, “How big of a UV sterilizer do I need,” let’s discuss the variables you should consider before purchasing one.

What Factors Affect the Size of A UV Sterilizer?


Let’s start small and discuss fish tanks. Once you’ve decided to add a sterilizer to your aquarium, your next question might be, “What size UV sterilizer do I need?” Determine your sterilizer size by two things: your tank size as well as the flow rate of the pump.

Flow Rate: The rate at which water flows through a UV sterilizer determines its kill ratio. Flow rate is measured in gallons per hour (gph).

Choosing a sterilizer with the correct flow rate for your body of water is crucial. Algae and bacteria will be unaffected if water moves too swiftly through the system. If it’s too slow, the water will heat up, raising the temperature of the tank and damaging the UV lamp and any other life in the tank.

Most UV sterilizer manufacturers list their UV systems’ minimum and maximum flow rates at various wattages. You can see the flow rate of any Aqua Ultraviolet system in their product description. When choosing a UV sterilizer, the maximum flow rate of the unit should be greater than the tank’s total volume.

For example, if you have a 100-gallon tank and want to manage parasites, you’ll need a minimum of 18 watts of UV light with a maximum flow rate of 100 gph. In this example, you would want a 25-watt UV light with a 150-gph flow rate for this tank.

Type and Size of the Water Body: For a UV sterilizer to be successful in an aquarium, it must be the correct size. A small UV won’t cut it, and you’ll be disappointed with the results. Always ensure that the wattage of the device and the flow rate of water through it are appropriate for the size of your tank.

Furthermore, the appropriate wattage for saltwater, freshwater, and outdoor ponds differs.

As a general guideline, add 10 watts to your total for every 75 gallons of salt water and 10 watts per 150 gallons of fresh water.

Outdoor ponds don’t require a strong UV sterilizer because they receive daily sunlight, a good UV source. Ten watts per 1,000 liters of water works in an outdoor pond scenario.

Selecting UV Sterilizer Sizes For Your Tank Size


For your UV sterilizer to perform best, ensure the water flow rate adheres to the manufacturer’s guidelines. Not all UV sterilizers are rated the same; research which brand would be best for your aquarium needs, or just stick with the best and buy from Aqua Ultraviolet.

Now, let’s move on to what size you’ll need for various bodies of water.

Aquariums: If the first thing that comes to mind is “what size UV sterilizer do I need for my aquarium,” know that for any tank under 75 gallons, you’ll need an 8-watt sterilizer with a flow rate of 120 gph.

Residential Water Body: UV sterilizers rated in the 30,000-45,000 columns are ideal for the reef environment. In marine fish tanks (no reef or live rock), a UV sterilizer rated in the 75,000 to 90,000 columns will most effectively control fish disease. But this varies for salt water or fresh water.

Ponds/Water Features: Some people have many pumps in their ponds. In this case, you’ll need a UV sterilizer for each pump. Usually, ponds also require more UV sterilization because their occupants produce more waste, which results in more aggressive algae development. A highly-powered UV sterilizer will destroy the algae quicker than it grows.

Commercial Size: These bodies of water can contain up to 50,000 gallons. To effectively disinfect this volume, increase the UV light’s intensity. For every 1,000 gallons of water, you’ll need about 30 watts.

Based on the required flow rate and body of water size, Aqua Ultraviolet can provide the right UV sterilizers to ensure efficient disinfection. Get in touch with our team today to get the best deal available.

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For over three decades, Aqua Ultraviolet has been the premier manufacturer of ultraviolet sterilizers and bio-mechanical filtration.

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