This sterilizer is not going to do any good if you connect it to the output or intake of your canister filter. If your range is 100-200, I would recommend putting a Mini-Jet 404 on it, which I believe is a 100gph pump. Always aim for the bottom of the range or you'll just give them a tan.
And to answer your question, yes it will kill diatoms. UV
light is the universal killer. In the proper dosage it will kill anything known to man, if I'm not mistaken. It kind of makes you wonder why people go out to kill their skin on purpose at times.
92-gallon corner tank, 100lbs of LR
, 140lbs of sand, 250watt 10,000K MH
, 110watts of actinic PCs, Mag 7 return, custom refugium, AquaC EV180 w/ Mag 5
Female lyretail anthias, eyelash blenny, tomato clown, saddleback clown, firefish goby, 2 sand-sifting stars