I’m thinking you are over crowded now.
Just joshing. I have a 180 as well.
I have 3 tangs which includes a full grown Vlamingi. The 180 has a good length to give room to swim. Sailfin tangs get medium to larger, but I don’t see any reason not to add another tang. I personally like the kole and yellow tangs. Not a big clown fan. My anthias are nice. Cardinals the are usually nice and chill.
Blue throat triggers are nice. Flame angels, coral beauty, and bi-color are nice. For some reason I never had good luck with them though
There lot of choice. I like to spend hours just going thru online vendor fish lists to get ideas.