teach me about polyp extension

[Nano]

K sorry for the delay, coffee break is here finally. So the stock list is
6 line wrasse
2 Occ. Clowns
Bangai cardinal
Scooter blenny (dragonet)
I had a cherub angel but lost him in the tank move, he never nipped at anything though so I doubt it was him unless I just never saw it. But sps is as followsgreen birdsnest
Blue polyp birdsnest
Purple bonsaired convexa
numerous acros
salty nuts (is this an acro?)
Seems to be just the acros showing signs of little PE the salty nuts seems to have days with lots of PE and days with none. The bonsai is the only browned out one