UV Sterilizer For The Aquarium

Updated August 12, 2019
Author: Mike - FishLore Admin
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The aquarium UV Sterilizer is a water filtration device that uses an ultraviolet light bulb to kill microscopic organisms that are free floating in the water. Parasites, viruses, algae and bacteria (good and bad) are the type of things that are "killed" after passing through the ultraviolet sterilizing unit. UV sterilizer devices can be used on swimming pools, in liquid factories (think beer) and in the home aquarium. Some large water purification centers employ some sort of UV sterilization on the outgoing water. These sterilizer units are also sometimes used in outdoor ponds to help control algae growth and they seem to do a decent job.

aquarium uv sterilizer

When using a UV Sterilizer in a home aquarium, the UV unit should be placed last in the filtration line. You want to first filter the aquarium water through your mechanical filter and then run the water through the UV device before returning the water to your fish tank. By first removing the solids in the aquarium water with your mechanical filter (canister filter, etc), you are helping your UV unit to attain maximum operational efficiency.

The effectiveness of any sterilizer is determined by the UV bulb wattage, the age of the UV bulb, how clean the quartz sleeve is and the flow rate of the unit.

Sterilizer Light Bulb Importance

The effectiveness of the bulb will deminish with time and use. Manufacturers usually recommend replacing the bulb after 6 months. You can find units with bulbs anywhere from 8 watts up to as high as 130 watts. The higher the wattage of the light, generally the more effective it is. If you have a unit with a lower wattage then you will want to have a lower flow rate to get the most out of the unit.

UV Sterilizer Flow Rate

The flow rate of the unit is an important consideration. Flow rate is measured in gallons per hour (gph) or liters per hour (lph). While higher flow rates may be acceptable for killing algae and some bacteria, you will usually need a much slower flow rate to kill parasites. For example, a 15 watt bulb will usually kill algae and bacteria with a 120 gph flow, but you will need to lower the flow rate to around 75 gph for it to effectively kill parasites. Read the manufacturers recommendations for your particular unit for effective bulb wattage and flow rates.

Keep the Quartz Sleeve Clean

One thing that some hobbyists forget about is the quartz sleeve that the UV bulb slips into. You must clean this quartz sleeve periodically to remove any buildup in order to keep your sterilizer operating at peak efficiency. The better sterilizer units have a wiper with a handle outside the unit that allows you to quickly and easily clean the sleeve without taking the sterilizer apart.

Where can I get a UV Sterilizer?

Nowadays Ultra Violet sterilizers can be found in local pet stores and they can definitely be found online. Look on eBay or similar auction sites for good deals on second hand and even brand new units. Since they are very expensive, you will want to research the unit you're interested in getting before investing in one. Use a search engine to find reviews on tropical fish forums (we have a good forum here on FishLore, hint hint) and discussion boards. Since you will usually need to change out the bulb every 6 months or so, find out how much a replacement bulb costs. The replacement bulb price may help when comparison shopping.

Do I really need an Ultra Violet Sterilizer for my aquarium?

For indoor freshwater fish tanks that are well filtered and properly maintained, you really don't need one. Saltwater hobbyists may have a good excuse for getting one because of the high price tags for many of the saltwater species. However, most hobbyists really don't need one if they are doing things properly. Doing things properly would mean using a quarantine fish tank for new arrivals and performing frequent fish tank maintenance.

Outdoor pond keepers may want to invest in one to help control algae problems in their outdoor ponds.

Below is a video from BRS which does a good job of explaining how these sterilizers work.

References :

UV Sterilizer Comments

From: Adam
I was constantly fighting a brown slime algae problem in my reef tank for months despite having no detectable levels of nitrates or phosphates in the system and vigorous surface agitation to keep oxygen levels high and carbon dioxide levels low. I guess I could have had defective test kits but these readings were consistently 0 and I was still having these algae problems! I decided to try a sterilizer in my tank after reading how pond owners use them to control algae in their outdoor ponds. I figured it could only help my tank. Guess what, I noticed a difference after the first two days of using this sterilizer and the amount of algae in my tank has been under control since. I'm using the 15 watt Aquastep UV Sterilizer that hangs on the back of the tank. There are better, more expensive models but this one seems to be doing it's job nicely. Thanks in advance for posting this and I hope it helps others decide if they need to get one of these sterilizers.

From: Big Hotz
I could never keep tangs or angelfish and I always keep my water good. Two skimmers, good water movement and change water every week with Nutri Live Sea water. Ich would always infect their gills, next day belly up. Just lost an $80 flagfin angelfish, Yes it hurts. I have two new tangs a sailfin and a yellow. Both of them started to spot up on there body. I went to Petsmart and bought the green killer 24 watt UV sterilizer for 50 bucks and Omega One flakes with garlic. The next day clean like I just fresh water dipped them. First time having success without using chemicals and a hospital tank. I let it run at night when the lights go off, two much heat with 510 watts of lights. I don't know if it was the food or the UV but all of my fish seem to be a lot happier. I will run for two weeks and then turn off. I will let you-all know what happens. Hope This Helps!
PS: be careful about what pet stores tell you, they are out for the money. Learn from friends and good forums!