Welcome to Pond Boss.

Sounds like a mess. I'm not knowledgeable about plecos or armored catfish. Gulping for air would indicate an oxygen shortage/water quality issue often caused by too many fish or rotting vegetation. With the lack O2 nothing can work out.

Step one is to observe and keep notes. Step 2 would probably be to kill off/nuke everything and cast netting won't do much for you in an acre. That takes chemicals and a waiting period of about a year. The water is too warm right now to stock anything.

BTW, bread balls won't draw anything. Fountains don't aerate anything but are mostly ornamental.

How deep is it? Any way to talk to the previous owner?

It's not about the fish. It's about the pond. Take care of the pond and the fish will be fine. PB subscriber since before it was in color.

Without a sense of urgency, Nothing ever gets done.

Boy, if I say "sic em", you'd better look for something to bite. Sam Shelley Rancher and Farmer Muleshoe Texas 1892-1985 RIP