I use the 3X on a 75 gal for 2 years and it worked great. I never had any problem with parasites. I would agree with the other posts....go big or go home. I have a 40 watt current on my 120gal now.
u had the 3x? I have a 250 gallon and my water is green...yikes!! so I was looking at the 12x. Just trying not to break the bank. This tank is a dang addiction. I know I can get a much more expensive uv...but trying to keep my addiction in check!!!!