Merdav, welcome to the forum! The best solution for breaking down the "muck" is a bottom diffused aerator, BUT, this is not the time of year to start one in a pond of your age, UNLESS you WANT to kill a bunch of carp and bullheads, and are prepared to restart with new fish.
The green sounds very good to me, brown would most likely be sediment suspension. If your goals and desires are to have the carp and turtles, it sounds perfect for that. If your desires are for bass CC and BG, some changes are probably in store for the pond.
The experts will want to know the pond size, all fish species (include length and body condition), depth, watershed size and if a stream feeds it. Pictures of the green would be a huge plus.
There is tons of info here to read with lots of pictures and ideas so welcome to the forum and soak up the knowledge and humor!
