Anchor Rode in salt water

I have my boat anchored out in salt water Puget Sound. I have 80 feet of chain and 40 feet of 5/8 three strand nylon (I think nylon). About every week I pull the rode, drop the chain on a float and go sailing.

I am getting a lot of green slim on the rode. When I wipe the slime off and rinse the rode, it looks like it is beginning to look frayed. Hmm...

Does anyone have any experience with the strength of rode standing in salt water? How long can rode stand in salt water and maintain its strength There is quite a bit of information on chain. I am thinking I may have to get more chain.

Walt