Remember that a goldfish is a carp, essentially. I'm not sure if that is the same as "goldfish minnows."

I would stick with fatheads and/or shiners.

Some of the goldfish (if that's what they are) will get too big to be eaten by the walleye, and carp/koi do stir up the bottom a little bit.

Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."