depends on the softie in question.
i usually don't get any/much grief from sarcos, lobos, caps, and nephts but sinularia and colts tend to coral fart, alot. even heavy carbon, Poly-Filters, and such can't keep up with them sometimes. i end up having to stick them in bigger setups to dilute their allelopathic issues. altho some sarcos can be very fartsy (e.g. spongiosum), while most others ime are innocuous.
room and placement will also give you "space". if the coral interprets a 'space shortage' (i.e. crowding) it'll react more often or severely. i've noticed a higher degree of mucus and coral farts if the coral feels (i believe) either another coral is encroaching, physically or chemically. i've actually seen chemicals exuding from the coral, it distorts the water like fw mixing with sw and trails off with the flow.