I have a 10watt Pondmaster UV sterlizer that I use in conjunction with a bio-filter in my pond. The manufacturer of the UV light suggests replacing it (the light bulb) yearly. Does anyone think this is necessary to replace it yearly? They are almost $50! How do I know when they have lost their effectiveness?

If you want the UV sterilizer to remain effective changing the bulb after twelve months of use is a must. A standard UV bulb only has a useful lifespan of about 8,000 hours. Remember, you need to change the bulb after twelve months, if you only use your pond six months out of the year, you could go two years without changing it.

Here's a link to an on-line business where you can get a 10 watt replacement bulb for $31.99 plus shipping and handling.

http://www.azponds.com/UV_parts.htm

I only use my UV lite for 4-5 days at a time, twice each year.

Mine should last alot longer.

I only use it when the water is green.

Once the water is cycled I don't need it anymore.

my UV is on 24/7 (except when i med) and i replace every 12 months, can't be too carful.

$50, is only about $4 a month.... it's like 0.13 per day?