It looks like gha to my eye. That'd suck up your nutrients and make sense to show 0 when tesying. Manual removal while increasing filtration and flow has workdd for me. Snails to clean what I missed. Cerith and big turbos worked for me (a few trochus too). Definitely beatable if you think logically about it; also tons of good info already on the forum I suggest looking for via search (perhaps worded better and backed by a bit more experience). Good luck!