Yazannreef
Valuable Member
Depends on how much you want to spend. What is your budget??
jesse88
Active Member
Miami Reef
10K Club Member
Don’t use the emergency badge unless it’s an actual emergency. 
BroccoliFarmer
10K Club member
Welcome to the R2R community!!!
I have used both of these and they are great. One requires replumbing while the other does not.
I have used both of these and they are great. One requires replumbing while the other does not.
Vyper
Active Member
It depends on what you want to use it for. Bacterial doesn’t take a lot but if you want to use it for parasites you are going to need a big one. I am running a 40watt and a 55watt on my 220gal. Both pentair UV‘s. Make sure to flow at speeds they require.
Quietman
2500 Club Member
At 120 gallon it's reasonably affordable to get one UV with constant flow to handle both algae and pathogens.
Plan on at least 8x turnover per hour (960gph) at min exposure for algae. This high turnover is to keep up with some species of dinoflagellate reproduction rate.
The high exposure for pathogens (ich for ex) is needed to kill or damage more complex organisms.
So looking at Aqua UV charts (don't buy filter that doesn't have flow/exposure charts) you can see a high exposure at 967 gph for a 40 watt unit.
Getting right sized pump to flow 967 gph with a closed loop set up (all flow through UV filter and not sump connection) will protect your tank from both constantly.
Changing any of the above will require recalculating flow needed at appropriate UV exposure.
Also note that at high end some state up to and over 120000 uw/cm2 exposure needed for some pathogens. You may wish to go with 57 watt unit.
Plan on at least 8x turnover per hour (960gph) at min exposure for algae. This high turnover is to keep up with some species of dinoflagellate reproduction rate.
The high exposure for pathogens (ich for ex) is needed to kill or damage more complex organisms.
So looking at Aqua UV charts (don't buy filter that doesn't have flow/exposure charts) you can see a high exposure at 967 gph for a 40 watt unit.
Getting right sized pump to flow 967 gph with a closed loop set up (all flow through UV filter and not sump connection) will protect your tank from both constantly.
Changing any of the above will require recalculating flow needed at appropriate UV exposure.
Also note that at high end some state up to and over 120000 uw/cm2 exposure needed for some pathogens. You may wish to go with 57 watt unit.
sunken3
Valuable Member
i like the 57W version.
Quietman
2500 Club Member
I do too and likely will use for my 75 build just because the form factor will fit in cabinet easier.
blaxsun
10K Club member
You don't necessarily need 8x turnover for your UV - not when the typical turnover for a system is 3-5x. I have a 57-watt AquaUV running 565 Gph which is a turnover of about 2.85x. This gives me almost double the radiation exposure for parasites.
