We are downsizing. Have had a blast with my pond. Have some lessons learned to share. For first 20 years, no problems with algae or weeds. Last 5 years though I've had to intervene. We've always had lots of geese- hundreds of them. It got so bad you could not walk around pond. I finally figured out the source of my problems was the geese and the goose poop adding too much nitrogen and phosphate . I have been keeping them at bay for last 2 years and it's making a difference. There is no silver bullet to cleaning out the pond, it has taken several years. Here's what I have done:
1. Keep geese away - I used to mow and string trim to edge of pond. Geese like that! They are lazy and can walk right in and out. I now leave a 2 foot unmowed strip around pond so there is no easy access

2. Algae and weed control - every year brings different weeds and algae, I think geese bring them in. A few years ago I had two types of pond weed take over! Never had seen it before. I used two aquicides/herbacides. Hydrothol and Prevent. Hydrothol is fast acting and worked within days. Prevent worked also. I have consistent outflow during rainy periods and the quick acting Hydrothol worked great. The Prevent is slow action and takes a couple of weeks but works well. I use it later in summer when outflow has stopped. I do have some u opened I will sell now that we are moving. I'll put me email at the bottom of this post

3. Manual weed/algae removal - I use a rake to manually remove as much algae and weeds as I can. Just killing it and leaving it in pond adds more nitrogen to pond and it comes back worse

4. Goose light - this away with geese blinking goose light has worked for me. Keeps geese away at night. Have found company stands behind their product. It stopped working last year. I called them and they sent me a replacement no questions asked

5. Pond dye/bacteria powder. - this has worked well. Turns water pretty blue color and the bacteria keep the algae down. It's expensive and because I have constant what're outflow it only lasts a couple weeks.

6. Muck removers- tried it, but no discernible difference. I found that raking bottom with a rake disturbs the muck such that the naturally present bacteria reduce the muck in the places I raked last year. I got a 16 foot pole and attached a garden rake head to rake as far out as I can. Also bought waders to wade out 4 feet And rake further out. Where I raked last year, it turns into sand next year.

7 temporary goose barrier - I went to Home Depot and bought 50 2 foot stakes and a string. I built a temporary barrier with stakes every 10 feet and two rows of string. That kept the geese out in winter

I have some unopened Hydrothol and Prevent I want to sell since we are moving. It's about $250 worth. I will sell for 125. I live in northern Virginia near Leesburg. Email me at tractor1home@gmail.com if you are interested and we can meet up. Guess I could mail it too. Will add pic unopened containers if I can figure how to do it. I bought enough for two applications but it worked well enough I only needed one.