For those of you in the know–could my koi possibly have died because it was entangled in plants and couldn’t surface for air? Haven’t found any info about this online.
You can barely imagine the stress on the other fish for one koi to die. They were huddled on the OTHER side of the pond, under the plants. Normally, they will eat from my hand but they wouldn’t even swim out to eat.
Little Green Bees 
Just stumbled on your site. Koi are extremely sensitive to their environment and if they don’t have proper filtration or a minor infection sets in, they’re pretty much done for. Most larger Koi ponds have a high-end filtration, the favorite being UV filtration. When I had a pond, my absolute favorite fish were goldfish from the bait shop. We have lakes here, so plenty of bait shops. They were extremely hardy, making it in the winter even after being frozen for a week. Koi are really pretty, but were too much work for my taste.
Thanks, Lindsay! We have a nice canister filter now–still no UV light but a heavy duty filtration medium with healthy bio-filter. We still have the one koi, who is doing well. Have five comets, a shubunkin, catfish, snail and three leopard frogs. So far, all is well. Just trying to keep the water cool during this hot summer! Thanks so much for the advice and for stumbling by! 🙂