This is my second koi pond in 4yrs and Ive ask myself whats best for clearing up the water from a dirty light brown silt look.

Pond is 9'x10' and 42" deep. apx 900gallons.

Well water only very soft and clear from the tap.

All was working great until I added some brown clay dirt to my lilly pots. Then a day later the water went light brown with about 4inch of visibility. Its been this way for about 2months now. Tried removing the dirt from pots but koi did it for me.

I have a 800gal pump with pressurize filter and 15watt uv cleaned every 2wks.

PH is little high but treat with acid weekly if needed.

6 - 12" koi all doing great.

Ive dropped the water twice by 30% and filled again but cant clear it.

Added 2 dose of bio-clarifier but nothing

Added a sludge remover but nothing

I do see a thick muddy look on the liner bottom so thinking about trying to vacuum it out as I think the koi sucked up the dirt looking for food. Just surprised it hasn't settled.

My only other thought is I noticed Robarb Spa Super Blue Water Polisher for pools. It says Non-Toxic Biodegradable.

Its some polymer for use in drinking water according to EPA

Link: http://www.poolstore.com/store1/welcome.html?chemicals/Robarb/SpaSuperBlue/index.html

I just dont know if this is bad for the koi.

I would think in a very small dose it would be ok

considering if you can swim and risk drinking it from a pool.