You've heard lots of very consistent advice from very knowledgeable people.
I'm not in their class, but I do have some experience and also say... For best results quickest, kill off and start over with a good plan.
Also, that wet weather creek... no chance it brings in bullheads, green sunfish and the like is there?
The intake from the ditch has a grate over it. The level of the ditch/creek doesn't hold a consistent level to hold any fish either. If it doesn't rain for a couple months, it will go dry
