IF there's any algae present, a stout dose (within labeled rates) of HYDROTHOL 191 might resolve both issues; and it's non-restricted in most states.
I like the way you think
Hydrothol 191 does do a pretty good job at killing pondweed and algae, and it doesn't take much to kill fish in small/shallow areas...even within labeled rates (don't ask us how we know)
But it is labeled as a algaecide/herbicide and not a fish toxicant, so to stay legal I would only use it if there is some algae or weeds present.
