Shelf life of UV bulb

Well, rear pond still isnt clear. Just for the heck of it, I purchased
an identical UV(half as many watts though @ 9 watts) for my front pond.
Just hooked it right up and didnt worry about the "proper
flow-through". Well, needless to say the front pond cleared up
completely in less than 48 hours. This wasnt even ran a continuous 48
hours. I had cut it off to clean the quilt batting and forgot to cut it
back on when I left for work. So....I have since put the smaller unit
on my back pond to see if itll do anything. Maybe this will let me know
if I have a bad bulb in the larger unit. We'll see....Also added a
prefilter around the pump, thats all i had for filtration on the UV
unit in the front pond and it seemed to work well enough.Now, if I can
just get my beautiful fish to move so I can see them in my clear water,
that would be great. They just keep hiding all the time.