I'm no sure what this is, he kind of poped up a few days ago, he/she is sitting right up on top of the rock kind of hard to see, unfortinatly my camera is not that good. i will try to get a beter pic as well.
That's for sure. Once they get out of control they can be very difficult to get rid of. I had a terrible majano infestation in my 240 gallon tank and ended up boiling all my rocks to get rid of them. It was literally like a carpet of majano.
Turn off the flow in the tank. You apply the stuff with a needless syringe. Cover the pest with it and watch it melt. Then turn everything back on. As long as you dont directly put it on the BTA you will be fine.