Lethargic fish

Hello I am new to this forum, I have had my pond for about 10 years and have never seen this problem. My fish won't come to the top, they stopped eating and now my water is pea soup green so I have no idea whats going on in there. I tested my water and my ph was high, (9) I got it to (8). Everything else tested great. I managed to pull one of my smaller fish out this morning, he looked fine, nothing on him, but he didn't put up too much of a struggle. I live in Reno Nv. My pond is 400 gallons. Any ideas on this would be appreciated. Thank you
p.s they are goldfish not koi

cleo1340

I would start with a 25% water change. The pea soup probably had little to do with this problem. Test the water chemistry for nitrite/nitrates. if they are high, another water change will help. Get a good bio filter.

Thank you Dr.Dave
This has been going on for about a month before the pea soup. I did a water change about 2 weeks ago and am going to do another this weekend. My nitrates were normal always have been, I know because I have been checking frequently. Thanks for the reply.