rusty screws!! How much cleaning needs done?

[Schulks]

I have had some unhappy corals for about a month so I've finally been checking my stainless steel parts.
These screws on top of my mixing containers had some rust so I've replaced them with some plastic screws I have.

bad steel screws.............................................................................good plastic screws

I also finally checked my float valve and it had some rust. I replaced that with a plastic screw but it has a metal pin at the top that doesn't touch water I can't replace but it looks ok. Should I just replace the float valve or is this probably good?





I'm adding fresh carbon right now to try and help.
To clean the water of the copper would polyfilter be good enough or should I use cuprisorb?

 

[KrisReef]

A little iron is not a problem. Polyfilter is enough if there are other metals that were present with the trash metal screws.