Iíve posted about my pond before: several thousand gallons, established for about a year now, with koi and rosy red minnows. Plants are hardy water lilies (I live in Kentucky, which gets pretty cold), water hyacinth, and water lettuce.
This spring and into early summer, the rosy reds were breeding like crazy. 20 adults became hundreds of healthy fry that were getting decent size and developing good color. Only one death that I saw.
Over that time, the floating plants took over big time and covered much of the top swimming space. Theyíve since been thinned out, but ever since that takeover, Iíve not seen any minnows near the surface. The adults preferred swimming in the deeper water generally, but the fry liked the shallow edges a lot.
What might have happened?
My parameters are solid (no ammonia or nitrites, <10 nitrates), algae is under control, and koi are fine. Other animals, like tadpoles and aquatic insects, are thriving.
Could something have eaten the minnows? Did the floating plants alter their habits to forage deeper?
I find it hard to believe that a mass die-off could have happened without being noticeable. The pond is a decent size, but itís not THAT large.
Any help is appreciated.