Need help eliminating nymphs in a pond

[HalJ]

Anyone know how to eliminate pond nymphs?  I’m in SoCal and have an 80 gal pond.  My white clouds were breeding like crazy, fry everywhere, then fish started disappearing.  I found some nymphs and removed them by hand.  I saw a video by Rachel O’Leary where she used Microlift for lice and anchor worms, which apparently interrupts the molting process.  After two doses I’m still finding nymphs.  Any suggestions?  I have plants growing above the waterline which eliminates the option for a cover.

[Pookies Aquatics]

Goldfish will eat nymphs, but they could eat your white cloud fry.

[Daniel]

The koi in my summer pond did a good job on eating dragonfly larva but a poor job on eating baby rice fish. The result was a population explosion of baby rice fish.