Can Koi coexist with many or any other types of fish in a pond and does anyone have any experience with this? To be a bit more specific, what about Yellow Perch, Brown bullhead, Minnows, Smallmouth Bass ect.?

Yes they can if they are large enough to escape predation. I know folks who have them for algae control. I don't think their fry will survive in a pond with predators because the colors really attract bass and such, probably perch also. I've been thinking about getting some too. I's like to here of other's experience in how well they control algae.

6 Koi in a clients 1/2 acre pond don't seem to do anything for the algae. I have to be careful treating it due to their copper sensitivity.

I had 20 KOI in a 1 acre pond that had predators LMB and never had any fry grow into larger KOI. With the 20 KOI, 6 Israeli Carp and large Channel Catfish I never had an algae problems. Pond friends in my area could not believe I controlled my algae with just fish.

Do you guys think you could have any kind of setup involving Koi and other fish where some of their fry do make it to adulthood? Would save restocking, sounds like LMB would be out but what about some other fish like Yellow Perch, Smallmouth Bass, Bullhead, Trout, sunfish ect. Surely some of the smaller fish wouldn't be able to predate all the Koi fry? I know they have fairly bright colors but they also lay a ton of eggs and i have also heard after a few generations in the wild the color reverts to the olive green of the common carp. Also heard they grow pretty fast. Would pond size and depth help any i wonder, large deeper ponds maybe allow some to reach adulthood.

Juvenile carp like to hide in weeds and plants.

Amount of cover will determine the survivability of hatchling carp and koi. Koi are just carp with fancy colors and or fins. some reproduction from koi will often be drab colored. IMO I would not want any reproduction from Koi that survive. Too many koi will easily make the water turbid and appear dingy especially if aeration is also present. Aeration mixes and circulates the roiled water produced by koi and carp.

I tossed 3 6" Koi into my pond last weekend, and finally spotted one a few days later. The one I saw was all threadbare and beat up, but still alive. It seems my existing fish don't like them there that much! I am guessing the Walleye are giving them grief, but who knows.