I’ll confess I’m not 100% up to speed on the terminology of these things, but I assure you I’ve used them for 5+ years and have experimented with several brands in several applications to maximize my benefit from them…
At the top of the page (first link) there is a chart listing uw/cm^2 ratings… 30,000 uw/cm^2 is what you get when you run this light at 700 gph, which is enough to kill green water (free floating algae) but not much more…
A very large percentage of the people I talk to who try out UV lights do not get a big enough light or they run it at too high of a flow rate… then 2 months later they run around saying that UV lights don’t work. Well if the user buys the wrong product for the job… it’s not the products fault… it’s the buyers…
The same chart to the far right lists 233 gph for 90,000 uw/cm^2 which is what they suggest to kill parasites & just about anything else…
The max flow rate at the far left of this chart is 1,800 gph, which is the maximum capacity that the housing can handle before leaking of risking damage to it’s internal parts such as the sleeve…
In the second link there is a chart which lists it’s max flow rate at 700 gph which is the maximum flow that the bulb will have any killing effect on anything… so for minimal effect use 700 gph…
I run my UVs at the rates I gave above (10 gph per 1W; 1W per 10 US gal of tank volume) and I trust that this rate kills parasites as well as clarifies the water (I’ve been working with Blue Dempseys for a couple years and they are prone to parasitic based illnesses)…
I’ve ran a 9W unit at 150~200 gph actual and I was not satisfied with it’s result…
I put an 18W on the same filter (150~200 gph actual) and was then quite impressed… I put the 9W on a PowerHead with an actual output of around 100 gph and was then satisfied, although the sleeve is now scratched due to particles being pushed through and it also requires cleaning much more often than when I use a filter as opposed to a powerhead… I could make many examples such as this working with UV lights as small as 5W and as large as 40W… on set ups as small as 10 gal and as large as 300 gal…
Again… I highly suggest using them in conjunction with a canister filter as opposed to a pump or PowerHead…