My experience with amanos is similar. I've made several improvements since the last batch died: added a spray bar, have a lot of flow for gas dispersal throughout the tank, 2/3 of the surface has small ripples while the other 1/3 has individual boils from the spray bar jets.
Recently I added a few amanos and ghost shrimp, drip acclimated, etc. The ghosts are active; the amanos stay hidden, assuming they're still alive.
PO4 10+ (burning off to 1-2 ppm)