As good as UV sterilizers are at controlling algae, bacteria and parasites, they are still rumoured to interfere with the natural food chain in your aquarium, indiscriminately killing phytoplankton and other microorganisms that may feed your fish or inverts.
This negative effect couldn’t be further from the truth. If it were to be believed then you would also be required to believe that our reef aquariums are alive with phytoplankton and waterborne organisms. Unfortunately, this is not the case. Our corals and inverts rely on the food we add, because those imagined phytoplankton and microorganisms do not exist at a level consistent enough to feed our inhabitants. Furthermore, we already employ the use of skimmers, filter socks and roller mats that do a good job of keeping the water clean. When feeding live phytoplankton it is always recommended to turn off the UV sterilizer for at least half and hour. This allows them to be gathered up by your corals and inverts. It is unfortunate that phytoplankton is unable to naturally proliferate in a saltwater aquarium, but our tanks simply cannot sustain their lifecycle.
You may also hear that a UV sterilizer can have a detrimental impact on the ‘good’ bacteria in a reef tank. When referring to ‘good’ bacteria, we are referencing nitrifying and denitrifying bacteria which are responsible the biological foundation of your saltwater aquarium. These bacteria reside primarily on and in live rock, sand and on surfaces. They do not remain suspended in the water column.
To summarise, a UV sterilizer in a saltwater aquarium can kill or sterilize whatever happens to pass through it, but it certainly does not starve your reef tank or disrupt the biological foundation.