the pigmys are not great sponge eaters, and in general even the most voracious sponge hunters rarely manage the invasive sponges you want. I have a venusta, who are notorious spongavores, and it won’t eat most invasive sponges, only the purple and grey, Not black or yellow. You can’t expect an angel, especially a xiphypop, to control sponge populations.
All the Xiphypops are of about equally reef safe. Which is largely down to the individual angel, some go wild on coral buffet and some are perfect citizens their whole life. It may come to, with any angel or benthic feeder: do I care more about this fish or this/these corals.
