Thanks! The UV is about 1 season (6 months of use) old. I will check
nitrate and ammonia.
George

"RichToyBox" wrote in message
. net...
George,

How old is the UV light. The bulbs will continue to glow, but the
intensity
falls off fairly quickly. They need to be changed at least once per year.
The rather low population of suspended algae should be being killed by the
UV if it working.

Do you have numbers for the ammonia and nitrites in your pond. I have
found
that when my ammonia jumps for any reason, I end up with green water.
Don't
know which came first or what the relationship is.
--
RichToyBox
http://www.geocities.com/richtoybox/pondintro.html


"George Rice" wrote in message
...
I would appreciate advice on how to eliminate the green tint in my pond
water. The water is "clear" in the sense that I can see the bottom but
the
green tint, which I assume is algae related, is not good.

My system consists of the following:
- A 4000 gallon concrete pond (with black epoxy coating) ranging in
depth
from 3 to 4 feet. We currently have about 15 large koi plus many
fingerlings
from recent spawns.
- A re-circulation system that includes a 36 watt UV light and a large
Cyprio filter (18 brushes and 12 foam filter blocks). I clean the
brushes
and foam blocks each week.
- The pond is in full sun much of the afternoon; but, about 35% of the
surface is covered by waterlilies.
- I treat the pond water according to the directions with "BZT
Aquaculture"
which is a brand of "microencapsulated bacteria & enzymes."
George