They are different kinds of sponges, nothing to worry about - very common in low light, low flow areas. But yeah, that strap isn't meant to handle saltwater for long term use.
dang I thought I was good with it being stainless. Which other would you guys recommend?
Regarding those sponges critters glad to know they are harmless, never seemed them before, they all came out in a week, because on last week WC I didn’t see them
You can get by with that for a good little while, but the salt eats away at the "stainless" properties over time... Here is an example of what I would recommend finding for a long term install: