Hi and welcome to fishlore
Your stocking list is really not good, hippo tangs cant go in a 55 gal need over 100 and thats for 1 ,, morish idols also need a 100 gallon tank and raarely survive in home aquariums as they normally starve them selfs and are very hard to keep,,, a chocolate star fish will eat fish and inverts if it can catch them ,,, and they normallt do when fish are resting ,
PLease read up on a fishless cycle for saltwater as you will need to cycle your tank,,
If you go with fake rock you would need a power filter and would work out at the same as buying
live rock ,, live rock is the best option for filtration in saltwater,,(power filters can become
nitrate problems) you would need power heads for water movement 10-20 x turnover
a protein
skimmer ,,,,
salt water test kits
hydrometer or even better a refractor meter for measuring salt mix
optional is a
RO/di water filter,, which will filter your water to take out chemicals and additives in your water that will cause problems within your tank like algaes ....
back to stocking a normal level of stocking is 1 inch of fully grown fish (measure the size it will grow to not the size it is put in) to every 16 liters of water so you have around 12-14 inchs for you fully grown fish so depending on your clowns you would have 6 inchs left this would give you a stocking of around 4 x 4inch fish ,,,
If you plan on keeping corals you will need good lighting for most so reasearch the needs of each coral before you buy or it can end up very expensive waste of money,,,