How is the correct size of a UV sterilizer determined?
This is about the only "complicated" part to the use of a sterilizer. For proper use, the UV sterilizer must be matched to the proper flow rate to ensure an efficient "kill dose" for the organisms you wish to eliminate. This flow rate must be matched to the size of the aquarium to ensure the proper number of "turn-overs" of the water. Most manufacturers will provide a table that recommends the maximum aquarium size and appropriate flow rate for each model they make. When comparing manufacturers, realize ratings may differ as to whether they take into account:
- Bulb efficiency: Some use 100 percent efficiency, others a lower efficiency (e.g., 60 percent observed towards the end of the bulb life)
- Organism to be killed: Bacteria/algae or protozoa
- Water clarity: Clear or turbid
- Transmission loss through the quartz sleeve
These differences make it very difficult to provide general rules of thumb. Check with the manufacturer if you are unsure on how the ratings are calculated.
How is a UV sterilizer installed?
The UV sterilizer should be the last piece of equipment in the system before the water is returned to the aquarium. It should be preceded by the biological and mechanical filters, and any chemical filter or heat exchanger in the system. Follow the manufacturer's directions on installation. Most units use hose barb connectors to attach to the appropriate water pump or are designed to allow add-on connectors as a PVC slip fit or hose barb attachment.
What is the proper maintenance schedule for UV sterilizers?
The quartz sleeve will need to be checked monthly and removed and cleaned with rubbing alcohol. Some larger UV sterilizers have wiper mechanism units installed for easier maintenance.
For most units, the UV bulb will need to be replaced after 6 months of continuous use, however, this time may vary so be sure to follow the manufacturer's recommendations. When installing or changing a bulb, never look directly at the bulb when the unit is turned on. Doing so can result in permanent damage to your eyes. (The damage can occur without you feeling any discomfort.)
Always disconnect the unit from the electricity when performing maintenance to protect against possible shock. When turned on, the bulb becomes especially hot when in the air and submerging it in water may cause it to break.
References and Further Reading
Fenner, RM. The Conscientious Marine Aquarist. TFH Publications, Neptune City, NY. 2001.
Tullock, JH. Successful Saltwater Aquariums. Energy Savers Unlimited, Carson, CA.1994.
Quality Marine. http://qualitymarineusa.com/drygoods/uv.html
