Is a UV Sterilizer Bad for a Reef Tank?

UV sterilizers do more good than harm in reef aquariums if used properly. UV sterilizers kill free-swimming spores and pathogens, making life safer for aquarium fish and invertebrates. However, reef tanks do depend on many microorganisms, like the bacteria that break down fish waste or the tiny crustaceans fishes and corals eat. Properly setting up your UV sterilizer can overcome such concerns.

  1. UV Sterilizers

    • A UV sterilizer is a piece of aquarium equipment that uses UV light to kill free-swimming microorganisms. UV sterilizers have quartz shields to keep the UV bulbs dry, since quartz does not filter UV light the way glass and acrylic do. UV radiation kills organisms by damaging their DNA. However, the UV light is emitted only within the sterilizer unit, where it can sterilize the water without hurting anything in the tank.

    Effectiveness

    • Some manufacturers of UV sterilizers boast a 99 percent kill rate of microorganism. However, this only applies to organisms that get run through the sterilizer. Some pathogens can live on surfaces or in fish, thus not spending enough time in the water column to get burned out. Still, UV sterilizers slow down the spread of many diseases, giving you more time to deal with them.

    Concerns

    • The biggest worry with UV sterilizers in the reef aquarium is that they may harm desirable organisms. Fortunately, the bacteria that perform biological filtration actually live only on surfaces in the aquarium. However, many reef aquariums are designed to try to encourage the growth of amphipods and other small crustaceans to provide food for fish and corals. Some reef aquariums even feature separate refugia to encourage the growth of these crustaceans. To deal with these concerns, always plumb UV sterilizers in such a way that their inlets are not near coral rubble -- the favorite abode of desirable crustaceans. You should also avoid plumbing your UV sterilizer on the same line as a refugium's outlet. Most refugia are plumbed in such a way that they drain into the aquarium, rather than going through a line, making this a moot point.

    Reducing Problems

    • Take a couple precautions when setting up your UV sterilizer to make it less likely that you'll kill off useful invertebrates like tiny crustaceans. First, put your drain lines near the top of the aquarium only, far from the sand bed and live rock rubble. This makes it less likely that it'll suck up any useful critters already in the aquarium. Second, make sure you don't plumb your UV sterilizer on the return line from your refugium, assuming your refugium has a return line.

    Danger

    • UV radiation can harm you if you use a UV sterilizer wrong. Always follow the manufacturer's instructions to the letter when using one. Never turn on the unit when the protective cover is open. Make sure the power is off the bulb when it's not in the sterilizer unit. Ultraviolet radiation can burn skin, blind you and cause skin cancer. Use caution when using them.