I don't see a problem with throwing everything back in. Fish die, there is no garbage man to come and remove them from the pond, they just complete the circle.
At my last place I threw everything I cleaned back into the pond, in the creek channel where our fishing dock was. At least 100-200 pounds of fish (live weight). I just figured I was chumming for the cat fish, although I think the turtles may have gotten more of the food. Before I moved the water was down over 6 feet (I think he had leak in that pond, told me it was the builders first time). I could walk across the creek bed in front of the dock where there had been 4-5 feet of water before and where I dumped all my cleanings. There was no sign of remains, no bone piles, nothing.
I wouldn't hesitate to put some deer or other carcasses in either, as nature does the same. At the same pond one winter the neighbor checked to see if we still had our dog, as something had made it to the center of the pond before falling through the ice. I went out and checked the tracks and it turned out to be a deer. Probably fed some critters for a while.
I actually wanted a high powered/big a** grinder to chop things up to feed the fish nice high protein feed. Most pond Bluegill I've seen will eat anything.
Now if I was cleaning commercially I might be careful about overloading the pond, but if it came out of the pond, it goes right back in.
Also in a real small pond I would not add much/any outside matter, but still can't see a small amount fo fish cleaning making much of a difference.

I am in the planning stages of a cleaning station for Pauls place right now (just found a Utility sink I have laying around, now all I need is a water pump and a battery, gotta keep looking).
I will start another thread when I get to it.
It will be at the edge of the pond and all cleaning will go right back into the pond.

Matt Wehland