So be wary of wasting your money on these, no matter how appealing the $30-$50 price for a UV Sterilizer combined with a filter that hangs on the back of your aquarium. In reality, these nothing more than basic filter with a pretty blue light inside them!!
Aquarium - Before and after using UV clarifier - YouTube
• Perfect New 36 Watt UV Sterilizer Light Water Clarifier Lamp Ultraviolet Filter with Bulb Tube Power Adapter for Aquarium Pond Tank Gold Fish Reef …
Aquarium - Before and after using UV clarifier
• Perfect New Fish Tank Aquarium 528 gph 13W UV Sterilizer Submersible Filter Pond Pump CUP-613 / UVCP-13 Fresh Water or Salt Water
• Dimension: 12.5" L X …
Having an UV Light on ANY aquarium can be a GREAT thing
Aqua Ultraviolet’s UV Sterilizers have been used by public aquariums, importers and hobbyists alike to control bacteria, protozoa and parasites, reducing the spread of fish disease. In a confined environment like an aquarium UV and filtration are essential. When using a UV Sterilizer in a home aquarium, the UV unit should be placed last in the filtration line. You want to first filter the aquarium water through your and then run the water through the UV device before returning the water to your fish tank. By first removing the solids in the aquarium water with your mechanical filter (canister filter, etc), you are helping your UV unit to attain maximum operational efficiency.
The aquarium UV Sterilizer is a water filtration device that uses an ultraviolet light bulb to kill microscopic organisms that are free floating in the water. Parasites, viruses, algae and bacteria (good and bad) are the type of things that are "killed" after passing through the ultraviolet sterilizing unit. UV sterilizer devices can be used on swimming pools, in liquid factories (think beer) and in the home aquarium using an aquarium UV sterilizer. Some large water purification centers employ some sort of UV sterilization on the outgoing water. These sterilizer units are also sometimes used in outdoor ponds to help control algae growth and they seem to do a decent job.The plus side to these submersible UV Pump/Filters is the need for no additional plumbing in aquariums or ponds, not that splicing a line for a TMC or Terminator UV is all that difficult (with ponds though, extra devices such as UVs can sometimes be a bit more of a plumbing project).
However the another entry into the field of Internal UVs are still incorrect as per their flow rate (& construction); The AquaTop UV Sterilizer Pump 3, 5, 7, & 9 watt are actually no better than the Submariner or similar early generation Internal UVs (please read more about these later in the article).