The Magic of UV Sterilizers

After a few months of a serious green water problem, some more experienced aquarist friends suggested installing a UV sterilizer.  I don’t know very much about aquariums generally, but from what others have said and from a little research I’ve done, there aren’t any big downsides to using the sterilizer.  The appliance “utilizes a germicidal fluorescent lamp that produces light at a wavelength of approximately 254 nanometers (2537 Angstroms). … As the light penetrates the bacteria/algae, it mutates the DNA (genetic material), preventing growth/multiplication of the organism.” They can be used in salt and fresh water, and do not pose a threat to coral, inverts, fish, or plants in any direct way.  The only thing that I am concerned about in my tank is that the Paratocinclus algae eaters will have less food. There’s still a decent amount of algae growing on plant surfaces, so hopefully that will be enough. The sterilizers need to be cleaned monthly and the bulb needs to be replaced about once a year, but the appliance and the bulbs are very affordable. This was a sort of last resort because the water changes were not working, and the water was so green I couldn’t even see the fish. Prior to this, I was supplementing with various prime products to introduce good bacteria and balance the water but it had no noticeable effect.

It’s been nearly a month now and the water remains very clear.  Prior to this, I was doing aggressive water changes and after only a few days the water would be cloudy and green again.  The UV sterilizer provides quite a bit of water movement which the fish seem to appreciate.  [R]The sad state of affairs before the UV sterilizer- photo was taken only one week after a 90% water change.  [L] one week after installation of the sterilizer.


The model being used is a 5W Sunsun that has a flow rate of 132 gallons/hour.  It is silent so long as the water level remains close to the top of the unit (there is a blue elbow that needs to remain out of water).

These Paratocinclus sp. Peru like to hang out on the Bolbitis where the flow is high. They are eating Spirolina logs, Spirolina powder, and algae that grows in the tank.


2 thoughts on “The Magic of UV Sterilizers

  1. If you would like to delve into aquarium keeping in a form that emphasizes natural balance and diversity, Dr Walter Adey has a three volume series of books called Dynamic Aquaria. As a researcher and head aquarist at the Smithsonian he writes in amazing detail about the ecological systems he worked with. But a tank as small as yours is very hard to manage in such a way. Thanks for the tip on your UV sterilizer – I’ll definitely be looking for one. Can’t seem to find an icon that will let me log in.

    1. Hi Brian,
      Thanks very much for the recommendation. I recently took this tank apart and turned it into a terrarium, but would eventually like to get a nice big aquarium going. Not running a filter was the demise of this tank I think. Do you keep fish?

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