Wow I haven't seen anything like that before!

Nasty...

Mine looks similar to that after only 4 months of using IO. When I used to use Reefers best, I rarely had any of the brown slime build up...but IO is disgusting.

ya dez mine is t hat too.

same here with instant ocean. what kind of salt do you use Dez?

And how did that work out for you?

Yes, Dez, my tub looks exactly the same. Cleaning that out is a pain in the ass. I used to try to do it monthly but have mostly given up. I just let it be.

I think your'e seeing that because it's a static basin that salt water is being mixed in before being moved somewhere else. I've been using H2Ocean for the past year. I keep a 44 gallon rubbermaid of it in the garage that I use for water changes on the pico tank, but do all my water change steps (including mixing of the salt) for the big tank in a dedicated sump chamber that gets put back online with the rest of the system when I'm done.

The rubbermaid is rapidly developing a gross crust just like that, but the glass of my water change sump chamber is as sparkling clean as the day it was built. Whatever does precipitate out of your salt during the mixing process falls out of solution in a separate basin like that and stays there, but if it's mixed in a vessel that will then go inline with a bigger system of water circulation, the precipitate will eventually dissolve back in to solution.

Does vinegar dissolve that gunk you're seeing?

I mix in a black bucket with IO.
I get the precip buildup but no brown crap.
Just rinse it out good once in a while or let it soak with vinegar.