Looking for a large sterilizer for my 400g tank.
Currently have a Coralife 36watt at only 240gph on my 125g working great.
I like the idea of low gph to provide maximum "dwell" time past the uv bulb.
what uv light would you guys recommend to provide similar dwell time at around 600-1000gph
This is a great article on UV sterilization.
http://www.americanaquariumproducts.com/AquariumUVSterilization.html
Especially helpful is this chart:
Based on the chart, you are somewhere between Level One and Level Two sterilization. While you have the wattage, your turnover rate is too slow for Level Two sterilization. By increasing your turnover rate to 3x an hour (flow rate of 375 gph), according to the chart you will have achieved Level Two sterilization if you have a high exposure UV. If it's not a high exposure UV sterilizer, you would need at least 46.88 Watts (375 gph/8 gph per Watt). Most of us don't even attempt Level Two sterilization--we settle for Level One sterilization.
To achieve Level Two sterilization on your 400 gallon tank at a turnover rate of 3xs, your flow rate would have to be 1200 gph. At 8 gph per Watt, you would need a 150 W UV sterilizer. At the same time, a flow rate of 600 gph would give you a 1.5 turnover rate on your 400 gallon tank. At 20 gph/Watt, your 36 W UV sterilizer (at 600 gph) would provide Level One sterilization on your 400 gallon tank.
So to calculate the Wattage, you have to consider the turnover rate for what you want to accomplish--that will give you the minimal flow rate you need, especially if you are considering Level Two sterilization. Level One is a slam dunk. Level Two is very difficult and spendy, and according to the article, most likely unnecessary for most of us fishkeepers.
