Personally go w a dwarf lion. My zebra started on live ghost shrimp, but quickly transitioned to frozen prawns, krill, small frozen sw fish. I started by hand feeding him live shrimp them mix in a prawn. Eventually only feeding frozen prawns
welcome to sw.
Now the big questions. How did you cycle the tank? Thats alot of fish for 54. The lion will eat your gramma and possibly the anthias.
Sw is much different then fw. Far less fish in a tank compared to fw. Very slowly add fish. Such as 1 or 2 fish a month.
Also live rock is dam...
Lets start with the sand. If you have that much food left in the sand you don't have enough flow. You need some power heads to circulate the water and keep that stuff in the water column. Then whatever isn't eating gets removed by filtration.
2nd the trigger. If its eating it should be fine. I...