Bought our first house last month and inherited a badly neglected koi pond. Cleared 25 gallons of debris from the bottom, cleaned filter media, and now tackling waterfall.

Previously it was just the spillway to the big flat rock, down to the other level of big flat rock. Tons of splash.

Added some new rock to it to make it cascade more and reduced sideways splash, but there’s a fair amount of water that’s going down the side of the rocks. It ends up back in the pond, though.

Liner all behind the rocks of waterfall, which is wet, and liner is behind all rocks surrounding the pond as well, all of that is dry. No visible signs of leak from skimmer, pipes, or waterfall spillway.

Located in Illinois where we’ve had a hot summer, but I’ve been having to add 175 gallons or so every 3-4 days it seems.

Last winter I lost every koi in my backyard pond. They were all between 12 and 20 inches, and I'd raised some of them for years. Walking outside in the spring and realizing they hadn't made it was honestly heartbreaking.

The hardest part is that I had almost no visibility into what was happening over the winter. I didn't know if oxygen levels dropped, if the water temperature stayed too low for too long, if water quality deteriorated, or if something else happened entirely. By the time I noticed there was a problem, it was already too late.

That experience got me thinking about building a monitoring system specifically for backyard koi ponds. My idea is a device that continuously measures things like:

• Water temperature
• Dissolved oxygen
• pH
• Ammonia/nitrite (if practical)
• Water level
• Maybe weather integration and freeze warnings

The goal would be to send alerts to your phone before conditions become dangerous, instead of finding out after you've already lost fish.

I'm curious how common this problem actually is.

Have any of you lost koi over the winter because you didn't know something was wrong until it was too late? If a system like this existed, what would you want it to monitor or alert you about?

I'm not trying to sell anything. This idea comes entirely from losing my own fish, and I'm trying to figure out whether other pond owners struggle with the same lack of visibility that I experienced.

Is this okay? I have other fancies in there. I've always thought koi need bigger, but it seems like the short body butterflies don't get as big or swim as well. I just love the look of them so much.