I have this on order for my freshwater Malawi tank. Did you get this? What pump/flow rate are you using?
I've had this for about a year now on a 100gal saltwater. Got it because replacement parts are easily accessible and the specs seemed comparable to others that are 4 times the price. The data sheet says the 13w should be 150-400 gph flow rate so I try to go with the slower one to attempt to catch more pests than algae.
I've had it on the entire time and have had no outbreaks of disease or cyano. But I can't really confirm that the uv is why. I submerse it in the sump, it gives me peace of mind that if the pump stops working there will still be water inside so it won't immediately melt. I also try to keep the in and out flows to different locations of the sump so it doesn't keep recycling the same water.