somehow the forum has a glitch yesterday and today as attached files are not allowing me to open them and view them.

How does your pond hold water in the summer? IS there quite a bit of water fluctuation? Do you have groundwater coming in to replace water during the non-spring months?
We have a fair amount of iron in our ground water and iron sediment makes our leaves and dirt carry a rust/brown color as the iron settles out. It hurts nothing, the fish don't mind.

I also have a smaller pond and I get a lot of hardwood leaves in it in the fall. I spend a fair amount of time raking out as far as I can reach every spring. This gets rid of lots of nasty brown muddy debris, dead algae from the year before and removes biomass, biomass that the algae will feed on the next season. I figure I can remove easily 600-800 pounds of biomass every year. Without that I think my algae problem would be big!!

There are those who have had some success with adding healthy bacteria and muck dissolving pellets. I have not tried that. I'm not sure how much that adds beyond the aeration you are doing, but some say getting muck dissolving pellets right down into the sediment on the bottom helps to some degree.

If your pond is 25 years old then you probably just have too much accumulated phosphorous and nitrogen packed in the sediment on the bottom. Ideally you would muck out with long reach excavator, but you may not get to the bottom at 20' deep. Access and cost usually is an issue too.

What type of aeration set up do you have? Maybe you can see some gains there?

Also, running an outboard motor (or better yet have someone dunk a jetski in there) to stir up the bottom sediment and really get things swirling can really help get oxygen into the bottom sediments. Think of all the kids walking in the same direction around the edge of the swimming pool and how the sediment all goes to a very tiny spot in the middle of the pool. Do that with a jetski and you can really stir things up.

For fun we had my teenager take our quad around the edge of the pond one summer day. His brother was on a wakeboard with a short rope, about 6' behind the quad. The wakeboard going round and round about 10 times was enough to uncover and sweep clean all the rock in the shallows as if I had power washed it. I'm sure this helped with aeration too.

You could have a fun experiment and when the water hits about 55 you could stock 20-30 pounds of tilapia if you can find them. They may help you to some degree too. Biggest help for me though was controlling phosphorous going into the pond and raking the perimeter fall and winter.