Should I be concerned? Can I just scrape away? Small round disk shaped started with on wall and small (first photo) it grew and also are in other places in tank now. Heavily planted and lots of wood. 74 degree water. Test attached. 5 angels 6 corys and two plecos. Probably too many hours of light per day. Auto feed extreme nano, once-twice week baby brine, new life spectrum tropical pellet occasionally, nightly switch(bug bite, algae wafer, repashy)