Not died, dyed.
I’ve been having issues with algae in the pond. I dug it too shallow (18" or so) partly because it’s so near the neighbor’s fence. I upgraded the pump and filter both, but because the shallow water is getting warmed by the sun all the way through, string algae is a problem. I decided to “solve” the problem by adding dye to the water. It’s supposed to inhibit algae growth by limiting the amount of light that gets to the nasty green stuff.
It was weird pouring it in, because it didn’t completely mix with the water at first, so there was a cloud of inky blackness like an frightened octopus was hiding under the bridge. I stirred it around a bit (brownian motion was too slow) and it seems to be OK. The filter isn’t filtering it out, at least.
Interesting stuff. I’ll post an update in a couple of weeks when I see how effective it is.