Determining Proper UV Wattage

[Pakman2]

I’m looking for some assistance in helping determine the proper sized UV for my tank. My current tank is a 75 gallon with a 20 gallon sump. Thank you again for all of your advice!

 

[miPapareef]

It really matters what you want to kill with the UV and how much flow you plan to run through it? Algae and bacteria takes a lot less than dinoflagellates and Protozoa.

I wanted to kill dinoflagellates in a 75 gallon, so I bought a 40W pentair smart UV and ran the flow rate at 170gph