no filter socks are normally white, google filter socks and you’ll see.
Filter wool is maybe an option for you instead, either one is good as it removes the nutrients before they break down adding PO4 and nitrates.
If the black thing you mentioned is some kind of filter, then that will not be helping and maybe adding to the problem, they need to be cleaned every 2-3 days and they are not as good as socks or filter floss as they let big particles through, socks and filter woll filter out much small particles, so I would change over to one of those.
A skimmer does similar to socks but removes much small particles, in your size tank you may not have room for a good one, they are not needed so don’t worry if you can’t fit one in, you just need to keep up with water changes and changing the socks or wool,often to make up,for not having a skimmer.