Inherited a pond with new house - HELP!

[j.w]

@Wallace
Whatever you choose to do, save as much of the old water as possible. It will give the fish a better chance at surviving instead of being shocked by too much new water. The fish is used to the old water.

 

[brokensword]

and realize if you take out a lot of your plants, the heron will more easily see your remaining koi. I'd seriously consider how you're going to protect what is left as well as anything else new you add to your pond. I'd make something that I could lift off (a framed net) when I was around and easily slide/put back when I'm not around.