I have a 16-gallon aquarium with 20 pounds of live rock, 4 small fish, an
Eheim 2213 and a 9-watt ultraviolet (UV) sterilizer. I run the UV sterilizer continuously, but ... do I need to?

There are two schools of thought on how frequently a UV sterilizer should run in a saltwater, and especially reef, aquarium setup. The first is to run the UV sterilizer 24/7: UV sterilizers are designed to run all day every day and doing so will certainly help control free-floating algae and parasites.

The thing is, UV sterilizers will not only kill "bad things." Populations of pods and other micro and macro organisms that are desirable in a reef aquarium will also be killed during their planktonc (free-floating) stage when they pass through a UV sterilizer.

That's why some reefers run their UV sterilizers part time. Maybe they'll only run it during the day or have it on one week and off the next. Some run UV sterilizers during the first few weeks after adding new specimens to their aquarium.

It really is one's discretion how often to run a UV sterilizer. I suggest part-time for a reef tank and 24/7 for a fish-only (FO) system.

If you would like to ask Keith a question, click here.