How many watts UV light for my 4 ft tank?

[equidorz]

can can any one tell me what is the difference between the different walts of uv light? i saw at c328 they have uv lights with different walts some 9walts some more. mine is a 4 ft x 1.5 x 1.5 tank.

[tawauboy]

it's watts.
this tells you how strong as well as the electricity consumption of the light.

[equidorz]

oh ok ok thanks for the reply. watts it is, sorry for my bad english! by the way does it matter what watts is suitable for a 4 ft tank? or any watt will do?

[Eralf]

Hmmmm... Actually, the wattage you'll need would depend on the flow rate of the water going through the UV filter, not really tank size.

Micro-organism would only be sterilised if they are exposed to sufficient UV radiation. To do that, you either make them stay in the UV tube for longer period (i.e. slower flow rate) or use a higher wattage lamp and zap them with more radiation as they zoom through.

I'm not sure what's the values, but on http://www.drsfostersmith.com/pic/ar...?articleid=440
it's stated as:

UV Bulb          gph to Control      gph to Control
 Watts)          Bacteria and Algae      Parasites
4                      60                  N/A
8                      120                 N/A
15                     230                 75
18                     300                 100
25                     475                 150
30                     525                 175
40                     940                 300
65                     1700                570
80                     1885                625
120                    3200                900
130                    3400                1140

Though manufacturers' recommendations will vary, 
the above chart provides a general idea of the wattage 
and the corresponding flow rates required for the control 
of bacteria, algae, or parasites.

[Shadow]

from the table seems like only 15Watt and above can kill parasites. Algae and bacteria are easier to kill

[Aquaculture]

OMHO, the size of your tank doesn't really affect on the voltage of UV. Presuming that you know the effects of using a UV lamp, I would strongly recommend you to use at least 13W and above to really have an effect on treating the water.