I have a half acre pond that I added muckaway a couple weeks ago, but I'm about to add fish this weekend and my question is its still approx. 6 inches of muck still there will this interfere with the fish like blue gills spawning

What size fish/species of fish are you adding and what is the substrate below the muck?

The BG will likely just move to more shallow water to find less sediment to lay their eggs. I don’t think you have anything to worry about. You could add some pea gravel in the shallows to facilitate a suitable substrate if you feel the need.

If possible, remove the muck from a small shallow area and add gravel. BG will likely spawn anyway but would be more successful with a good spawning area.