The pond water has been green, green, green. So green we can't see the fish very well. The fish don't care, and the green water protects their skin from the sun. But we can't see them. I added some algae killer to clear it up.
I got a new UV unit to replace the old one, so I won't have to use algae killer. The koi seem to tolerate the chemical just fine, but I dislike using the stuff. The old UV unit worked fine and dandy when the pond was half the size it is now, but since the remodel it no longer does the job (even with, yes, a brand new bulb). The new UV unit is supposed to be effective at a much higher flow rate, which is what is needed to solve the problem (I think, I hope).
The problem is in the red oval below (lower left corner of photo). I must figure out how to fit the new one in the same general configuration. The new UV is much longer than the old one. I have some thinking and planning to do, always a challenge. The UV is on the bottom drain circuit. There are two filtration circuits on the pond; one is the bottom drain circuit and one is the skimmer circuit.
Dirty water goes down the ponds' bottom drain, into the Sieve which cleans out the larger bits like Koi poops and algae clumps. The water is then pushed by a pump through a bead filter, which removes smaller particles and also provides a large amount of surface area for beneficial bacteria to colonize. The bacteria consume ammonia in the water and convert it into nitrates. Other bacteria convert the nitrites to nitrates. Ammonia and nitrites are deadly to koi; nitrates much less so. But back to the circuit...after the bead filter, the water flows through the UV unit and then splits into two different returns to the pond.
The skimmer circuit takes water from the top of the pond via the skimmer. It goes to a pump, which pushes it through another bead filter (more beneficial bacteria colonies), to a shower filter. The shower sends the water back into the pond. The shower contains more media for more beneficial bacteria colonies, and the showery flow also aerates the water for happy, happy fish.
So I'll be struggling with pond plumbing for the next few days. In the meantime, it's so good to see something of the Koi besides their mouths open for dinner.