A temporary solution, that you could do right now, would be to toss in
a bunch of calcium bentonite clay, while your system is circulating.
You should be able to find this at any koi supply place. Don't be afraid
to use treble or quadruple what they recommmend. Expect muddy water for
a day or so, nothing wrong, to be expected. Then everything should clear
up, see all the way to the bottom type of stuff.

What does the bentonite clay do???

Calcium bentonite is similar to the ingredenients of kitty litter.
It's both absorbant and charged. Suck. Zap. Everything dissolved in
the water, now in the bentonite. As a bonus, it also releases trace
minerals into the water, that the koi like. Google for it.

C//