There are lots of pond topics to study and learn about. Use information in the threads of our Archives section.
https://forums.pondboss.com/ubbthreads.php?ubb=postlist&Board=22&page=1I will provide opinions on a few of your items.
1. IMO the use of the copper sulfate (CuSO4) in one of several possible ways IMO contributed to the dead fish. Copper (Cu) is a heavy metal and as with all heavy metals they are stable in the environment. Once in the pond Cu based compounds do not go away nor decompose. Every handful that has been applied in the past is still present in the bottom sediments. Then the bound copper can and does accumulate in the pond bottom to eventually cause unhealthy sediments. In agricultural fields, 1-2 lbs of Cu per acre(ppm) is considered a high amount. I have measured Cu in ponds having 1000+ lbs/acre resulting in very very unhealthy harmful sediments. What does one do with Cu contaminated pond sediments? Probably the hazardous waste landfill. IMO use Cu products as a very last result. There are much better ways to deal with algae than using Cu based products.
https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92633#Post926332. “The longterm goal is to stock the pond and get it in great fishing fun shape! But I need to get the water safe first.
You are not going to do that with always using more copper sulfate.
Use information in the Archives for all about the topics of fish management.
https://forums.pondboss.com/ubbthreads.php?ubb=postlist&Board=22&page=13. “ I have read that an at home water test is expensive and not reliable. What's the most affordable and reliable way to test water? Can I bring a sample somewhere?”
What items do you want to be tested for?
4. Aeration. In addition to what Theo posted above.
Properly sized aeration helps keep dissolved oxygen on the bottom and throughout the water column. You probably know what happens to about all living things except anerobic bacteria when there is no oxygen. Aeration is very beneficial to better health of all living things in the pond and it helps quickly and cleanly decompose the organic slop aka muck in the pond bottom.
There are several ways to DYI pond aeration. You need a good air compressor that makes 3-5 cfm of air volume. Pond depth determines the needed pressure produced by the compressor. You need an air delivery hose from compressor to the bubbler(aka underwater air diffuser) and an air diffuser; most popular is a rubber membrane diffuser although there are all sorts of other forms of diffusers and even homemade air diffusers that can be placed on the pond bottom.
Again learn from our Archives Section.
https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92494#Post92494
