Fwiw - there are ways to modify steps like that to prevent algae from growing in them. Adding lots of holes for circulation & such. Along with ensuring any weights are completely sealed. If you want to try them again in the future we can help you sort that out. I gotta have my steps, my knees & ankles don’t appreciate a ladder one bit!
As for the deep clean it can be pretty helpful. It is a good idea to install unions for easy access/replacement of equipment. So if you have to cut pipes to access the sand add some unions.
The deep clean is something that should be done every couple seasons anyway.
& yes the sun wreaks havoc on high fc levels. the higher they are the worse this is which is one reason why it’s not recommended to go above slam level for your cya as it wastes chlorine. The ammonia problem consumed alot of that chlorine- this is not uncommon. It was extended a little because you added cya.
But, From now on you know that if fc is zero & so is cya to do the ammonia protocol
before adding cya so hopefully if it ever happens again (let’s hope not) it won’t be as thirsty for your liquid gold!
Try not to get discouraged by the day time losses, just stay on it, dosing as frequently as you can. Your overnight losses are getting better & better which means you’re getting there. As mentioned, sand filters can just take time to clear. You’re in the patience part now. It will come.
Not sure if this was mentioned previously but clean your beaker with alcohol & rinse it to be sure it’s not causing interference with the cc’s test. It’s seen alot of action over the last week