Btw I recently started carbon dosing only at 30 ml of vinegar a day in a 600 gallon system.. Water is super clear and phosphates down!!!! A lot! I feed heavy and incorporate this method along w gfo carbon and a. If skimmer. I don't plan on going over the 30 ml.. Read into it, I read on a ton of different sites..
Keep us updated w the socks
Have you consider using phos free to bring down your phosphate first? You need some low micron bags to use with the stuff, it works great to lower the phosphate and help with algae elimination.
What about using nylon filter socks. Did you try adding a brand new sock and than wash it. How long have you be using same sock? See if nylon sock work. They shouldn't hold as much phosphate. Putting sock in RO water in bucket will do nothing if sock is leeching phosphate. It's just sitting in it. If anything has to be rinised out with RO water. Do away with sock for a while and see if its is coming from socks.. Levels go down without socks?